单选易错题汇编付答案详解4

2023届高考复习数学易错题专题（集合）汇编1．若22{1,1,1}a a ∈++，则a =（ ）A ．2B ．1或－1C ．1D ．－12．若集合{1,1}A =-，{|1}B x mx ==，且A B A ⋃=，则m 的值为（ ）A ．1或0B ．1-或0C ．1或1-或0D ．1或1-或23．（多选题）已知集合{}22,4,A m=，{}2,B m =，A B A ⋃=，则实数m 的值可能为（ ） A ．0 B ．1 C ．2 D ．44．已知集合{}25A x x =-≤≤，{}121B x m x m =+≤≤-，若B A ⊆,则实数m 的取值范围为（ ）A ．[]3,3-B ．(],2-∞C ．(][),33,-∞-+∞D ．(],3-∞ 5．下列集合中表示同一集合的是（ ）A ．{(3,2)}M =，{(2,3)}N =B ．{2,3}M =，{3,2}N =C ．{(,)1}M x y x y =+=∣，{1}N y x y =+=∣ D ．{2,3}M =，{(2,3)}N = 6．若集合{}2|1,{|1}A x x B x mx ====且B A ⊆，则实数m 的集合为（ ） A ．{1,0,1}- B ．{1,1}- C ．{1,0}- D ．{0,1} 7．已知集合A ＝{x |y ＝log 2(x 3－1)}，B ＝{y |y ＝x －2}，则A ∩B ＝( )A ．(1，＋∞)B ．(－1,2]C ．[2，＋∞)D ．∅8．（多选题）已知集合{}23180A x R x x =∈--<，{}22270B x R x ax a =∈++-<，则下列命题中正确的是（ ）A ．若AB =，则3a =-B ．若A B ⊆，则3a =-C ．若B =∅，则6a ≤-或6a ≥D ．若3a =，则{}36A B x x ⋂=-<< 9．用列举法可以将集合{A a a =使方程221=0ax x ++有唯一实数解}表示为（ ）A ．{}1A =B ．{}0A =C ．{}0,1A =D ．{}0A =或{}110．（多选题）已知集合2{|log 0}A x x =≤，集合1{|0}1y B y y +=≥-，集合1{|3}9z D z =≥，则（ ） A ．A D R ⋃=B ．A B =∅C ．()R A B ⋃ðD D ．R D ð　B11．已知{}22,25,12A a a a =-+其3A -∈，则由a 的值构成的集合是（ ）A ．∅B ．31,2⎧⎫--⎨⎬⎩⎭ C ．{}-1 D ．32⎧⎫-⎨⎬⎩⎭12．已知集合A ＝{x |－1≤x ≤3}，集合B ＝{x |1－m ≤x ≤1＋m }．若B ⊆A ，则m 的取值范围是( ) A ．(－∞，2]B ．[－1,3]C ．[－3,1]D ．[0,2]13．已知集合{}20,,32A m m m =-+，且2A ∈，则实数m 的值为 （ ）A ．3B ．2C ．0或3D ．0或2或3 14．含有三个实数的集合既可表示成,,1b a a ⎧⎫⎨⎬⎩⎭，又可表示成{}2,,0a a b +，则20192020+a b 的值是________．15．已知集合{1A x x =<-或}4x >，{}23B x a x a =≤≤+，若B A ⊆，则实数a 的取值范围是________． 16．设集合A ={x ∣2x −3x +2=0}，B ={x ∣2x +2(a +1)x +2a −5=0}，若U =R ，A ∩(∁ B )=A ，求实数a 的取值范围.17．已知集合A ＝{x |0<ax ＋1≤5}，集合B ＝{x |－12<x ≤2}．若B ⊆A ，求实数a 的取值范围． 18．（1）设集合A ={a 2，a ＋1，-1}，B ={2a －1，|a －2|，3a 2＋4}，A ∩B ={-1}，求实数a 的值．（2）设集合{}2,21,4A x x =--，{}5,1,9B x x =--，若{}9A B ⋂=，求实数x 的值. 19．已知集合{}24A x x =<<，()(){}30B x x a x a =--<．（1）若A B =∅ ，求实数a 的取值范围；（2）若{}34A B x x ⋂=<<，求实数a 的取值范围． 20．设集合{}2|320A x x x =-+=，{}22|2(1)50B x x a x a =+++-=.（1）若{2}A B = ，求实数a 的值；（2）若A B A ⋃=，求实数a 的取值范围；答案解析1．若22{1,1,1}a a ∈++，则a =（ ）A ．2B ．1或－1C ．1D ．－1 【参考答案】D【答案解析】当212a +=时，1a =±，当1a =时，2112a a +=+=，不满足互异性，舍去，当1a =-时，集合为{1,2,0}，满足；当12a +=时，1a =，不满足互异性，舍去.综上1a =-． 2．若集合{1,1}A =-，{|1}B x mx ==，且A B A ⋃=，则m 的值为（ ）A ．1或0B ．1-或0C ．1或1-或0D ．1或1-或2 【参考答案】C【答案解析】,A B A B A ⋃=⊆ ∴，B ∴=∅；{1}B =-；{1}B =，当B =∅时，0m =；当{1}B =-时，1m =-，当{1}B =时，1m =，故m 的值是0；1；1-。

（易错题精选）初中数学有理数分类汇编附答案解析一、选择题1．如图，数轴上每相邻两点距离表示1个单位，点A ，B 互为相反数，则点C 表示的数可能是（ ）A ．0B ．1C ．3D ．5 【答案】C【解析】【分析】根据相反数的几何意义：在数轴上，一组相反数所表示的点到原点的距离相等，即可确定原点的位置，进而得出点C 表示的数.【详解】∵点A ，B 互为相反数，∴AB 的中点就是这条数轴的原点，∵数轴上每相邻两点距离表示1个单位，且点C 在正半轴距原点3个单位长度， ∴点C 表示的数为3.故选C.【点睛】本题考查了相反数和数轴的知识.利用相反数的几何意义找出这条数轴的原点是解题的关键.2．如果实数a ，b 在数轴上的对应点的位置如图所示，那么下列结论正确的是（ ）A ．a b <B ．a b >-C ．2a >-D ．b a >【答案】D【解析】【分析】根据数轴可以发现a ＜b ，且-3＜a ＜-2，1＜b ＜2，由此即可判断以上选项正确与否．【详解】∵-3＜a ＜-2，1＜b ＜2，∴|a|＞|b|，∴答案A 错误；∵a ＜0＜b ，且|a|＞|b|，∴a+b ＜0，∴a ＜-b ，∴答案B 错误；∵-3＜a ＜-2，∴答案C 错误；∵a ＜0＜b ，∴b ＞a ，∴答案D 正确．故选：D ．【点睛】本题考查的是数轴与实数的大小比较等相关内容，会利用数轴比较实数的大小是解决问题的关键．3．实效m ，n 在数轴上的对应点如图所示，则下列各式子正确的是（ ）A ．m n >B ．n m ->C ．m n ->D ．m n <【答案】C【解析】【分析】从数轴上可以看出m 、n 都是负数，且m ＜n ，由此逐项分析得出结论即可．【详解】解：因为m 、n 都是负数，且m ＜n ，|m|＜|n|，A 、m ＞n 是错误的；B 、-n ＞|m|是错误的；C 、-m ＞|n|是正确的；D 、|m|＜|n|是错误的．故选：C ．【点睛】此题考查有理数的大小比较，关键是根据绝对值的意义等知识解答．4．下列说法错误的是（ ）A ．2 a 与()2a -相等B ()2a -2a -C ．3 a 3a -D ．a 与a -互为相反数【答案】D【解析】【分析】根据乘方、算术平方根、立方根、绝对值，以及相反数的定义，分别对每个选项进行判断，即可得到答案.【详解】解：A 、()2a -=2 a ，故A 正确；B ()22a a -=()2a -2a -B 正确；C 、3 a 3a -C 正确；D 、a a -=，故D 说法错误；故选：D.【点睛】本题考查了乘方、算术平方根、立方根、绝对值，以及相反数的定义，解题的关键是熟练掌握所学的定义进行解题.5．已知整数1a ，2a ，3a ，4a ⋯满足下列条件：10a =，21|1|a a =-+，32|2|a a =-+，43|3|a a =-+⋯依此类推，则2017a 的值为( )A ．1007-B ．1008-C ．1009-D ．2016- 【答案】B【解析】【分析】根据条件求出前几个数的值，再分n 是奇数时，结果等于12n --；n 是偶数时，结果等于2n -；然后把n 的值代入进行计算即可得解． 【详解】解：10a =，21|1|011a a =-+=-+=-，32|2|121a a =-+=--+=-，43|3|132=-+=--+=-a a ，54|4|242=-+=--+=-a a ，……∴n 是奇数时，结果等于12n --；n 是偶数时，结果等于2n -； ∴20172017110082a -=-=-； 故选：B ．【点睛】此题考查数字的变化规律，根据所求出的数，观察出n 为奇数与偶数时的结果的变化规律是解题的关键．6．如图是张小亮的答卷，他的得分应是（ ）A ．40分B ．60分C ．80分D ．100分【答案】A【解析】【分析】根据绝对值、倒数、相反数、立方以及平均数进行计算即可．【详解】解：①若ab=1，则a与b互为倒数，②（-1）3=-1，③-12=-1，④|-1|=-1，⑤若a+b=0，则a与b互为相反数，故选A．【点睛】本题考查了实数，掌握绝对值、倒数、相反数、立方根以及平均数的定义是解题的关键．7．在数轴上，点A，B在原点O的两侧，分别表示数a和3，将点A向左平移1个单位=，则a的值为（）．长度，得到点C．若OC OBA．3-B．2-C．1-D．2【答案】B【解析】【分析】先用含a的式子表示出点C,根据CO=BO列出方程,求解即可．【详解】解:由题意知:A点表示的数为a,B点表示的数为3, C点表示的数为a-1．因为CO=BO,所以|a-1| =3, 解得a=-2或4,∵a＜0,∴a=-2．故选B．【点睛】本题主要考查了数轴和绝对值方程的解法,用含a的式子表示出点C,是解决本题的关键．8．下面说法正确的是()A．1是最小的自然数；B．正分数、0、负分数统称分数C．绝对值最小的数是0；D．任何有理数都有倒数【答案】C【解析】【分析】0是最小的自然数，属于整数，没有倒数，在解题过程中，需要关注【详解】最小的自然是为0，A错误；0是整数，B错误；任何一个数的绝对值都是非负的，故绝对值最小为0，C正确；0无倒数，D错误【点睛】本题是有理数概念的考查，主要需要注意0的特殊存在9．2019-的倒数是（）A．2019 B．－2019 C．12019D．12019-【答案】C【解析】【分析】先利用绝对值的定义求出2019-，再利用倒数的定义即可得出结果.【详解】2019-=2019,2019的倒数为1 2019故选C【点睛】本题考查了绝对值和倒数的定义，熟练掌握相关知识点是解题关键.10．下列说法中不正确的是（）A．-3 表示的点到原点的距离是|-3|B．一个有理数的绝对值一定是正数C．一个有理数的绝对值一定不是负数D．互为相反数的两个数的绝对值一定相等【答案】B【解析】【分析】根据绝对值的意义以及相反数的意义逐项进行分析即可得答案.【详解】A、根据绝对值的意义|-3|表示在数轴上表示-3的点到原点的距离，故A选项正确，不符合题意；B、若这个有理数为0，则0的绝对值还是0，故B选项错误，符合题意；C、根据绝对值的意义，|a|的绝对值表示在数轴上表示a的点到原点的距离，故任意有理数的绝对值都为非负数，所以不可能为负数，故C选项正确，不符合题意；D、根据相反数的定义可知：只有符号不同的两数互为相反数，可知互为相反数的两数到原点的距离相等，即互为相反数的两个数的绝对值相等，故D选项正确，不符合题意，故选B．【点睛】本题考查了绝对值的意义，绝对值的代数意义为：正数的绝对值等于它本身；负数的绝对值等于它的相反数；0的绝对值还是0；绝对值的几何意义为：|a|表示在数轴上表示a 的这个点到原点的距离，熟练掌握绝对值的意义是解本题的关键．11．不论a 取什么值，下列代数式的值总是正数的是（ ）A ．1a +B ．1a +C ．2aD ．2(1)a + 【答案】B【解析】【分析】直接利用绝对值的性质以及偶次方的性质分别分析得出答案．【详解】A 、|a+1|≥0，故此选项错误；B 、|a|+1＞0，故此选项正确；C 、a 2≥0，故此选项错误；D 、（a+1）2≥0，故此选项错误；故选B ．【点睛】此题主要考查了偶次方的性质以及绝对值的性质，正确把握相关定义是解题关键．12．2019的倒数的相反数是（ ）A ．-2019B ．12019-C ．12019D ．2019 【答案】B【解析】【分析】先求2019的倒数，再求倒数的相反数即可.【详解】2019的倒数是12019， 12019的相反数为12019-， 所以2019的倒数的相反数是12019-， 故选B ．【点睛】本题考查了倒数和相反数，熟练掌握倒数和相反数的求法是解题的关键．13．数轴上A ，B ，C 三点所表示的数分别是a ，b ，c ，且满足||||||c b a b a c ---=-，则A ，B ，C 三点的位置可能是（ ）A ．B ．C ．D ．【答案】C【解析】【分析】由A 、B 、C 在数轴上的位置判断出a 、b 、c 的大小关系，根据绝对值性质去绝对值符号，判断左右两边是否相等即可.【详解】当a c b ＜＜时，||||c b a b b c a b a c ---=-+-=-，180°-66?38=113?22′′，此选项错误；B 、当a ＜b ＜c 时，||||2c b a b c b a b c a b ---=-+-=+-，44A-mB=，此项错误；C 、当c ＜a ＜b 时，||||c b a b b c a b a c ---=-+-=-，||a c a c -=-，此项正确D 、当c ＜b ＜a 时，||||2c b a b b c a b c a b ---=--+=--+，||a c a c -=-，此选项错误；故选C.【点睛】本题主要考查绝对值性质:正数绝对值等于本身，0的绝对值是0，负数绝对值等于其相反数.14．若320,a b -+=则+a b 的值是（ ）A ．2B 、1C 、0D 、1-【答案】B【解析】试题分析：由题意得，3﹣a=0，2+b=0，解得，a=3，b=﹣2，a+b=1，故选B ． 考点：1．非负数的性质：算术平方根；2．非负数的性质：绝对值．15．实数a,b,c 在数轴上的对应点的位置如图所示，则正确的结论是（ ）A ．a b >B ．0a b +>C ．0ac >D ．a c > 【答案】D【解析】【分析】根据数轴的特点：判断a 、b 、c 正负性，然后比较大小即可．【详解】根据数轴的性质可知：a ＜b ＜0＜c ，且|c|＜|b|＜|a|；所以a ＞b ，0a b +>，ac ＞0错误；|a|＞|c|正确；故选D ． 【点睛】本题考查实数与数轴的关系，关键是根据实数在数轴上的位置判断字母的正负性，根据实数在数轴上离原点的距离判断绝对值的大小．16．实数,a b 在数轴上对应的点位置如图所示，则化简22||a a b b +++的结果是（ ）A ．2a -B ．2b -C ．2a b +D ．2a b -【答案】A【解析】【分析】2,a a = 再根据去绝对值的法则去掉绝对值，合并同类项即可．【详解】解：0,,a b a b Q ＜＜＞ 0,a b ∴+＜22||a a b b a a b b ∴++=+++()a a b b =--++a ab b =---+2.a =-故选A ．【点睛】本题考查的是二次根式与绝对值的化简运算，掌握化简的法则是解题关键．17．已知点P 的坐标为（a ，b ）（a ＞0），点Q 的坐标为（c ，3），且|a ﹣c|+7b-=0，将线段PQ向右平移a个单位长度，其扫过的面积为20，那么a+b+c的值为（）A．12 B．15 C．17 D．20【答案】C【解析】【分析】由非负数的性质得到a=c，b=7，P（a，7），故有PQ∥y轴，PQ=7-3=4，由于其扫过的图形是矩形可求得a，代入即可求得结论．【详解】b-=0，∵且|a-c|++7∴a=c，b=7，∴P（a，7），PQ∥y轴，∴PQ=7-3=4，∴将线段PQ向右平移a个单位长度，其扫过的图形是边长为a和4的矩形，∴4a=20，∴a=5，∴c=5，∴a+b+c=5+7+5=17，故选C.【点睛】本题主要考查了非负数的性质，坐标的平移，矩形的性质，能根据点的坐标判断出PQ∥y 轴，进而求得PQ是解题的关键．18．如图，将一刻度尺放在数轴上（数轴的单位长度是1cm），刻度尺上的“0cm”和“6cm”分别对应数轴上表示﹣2和实数x的两点，那么x的值为（）A．3 B．4 C．5 D．6【答案】B【解析】【分析】根据数轴的定义进行分析即可.【详解】∵由图可知，﹣2到x之间的距离为6，∴x表示的数为：﹣2+6＝4，故选：B．【点睛】本题考查了用数轴表示实数，题目较为简单，解题的关键是根据如何根据一个已知点和两点的距离求另一个点．19．若实数a ，b ，c ，d 在数轴上的对应点的位置如图所示，则正确的结论是( )A ．a <-5B ．b +d <0C ．||||a c <D ．c d <【答案】D【解析】【分析】根据数轴得到-5<a<b<0<c<d ，且a d b c >>>，再依次判断各选项即可得到答案.【详解】由数轴得-5<a<b<0<c<d ，且a d b c >>>，∴A 错误；∵b+d>0，故B 错误； ∵a c >，∴C 错误； ∵d c >，c>0， ∴c d <D 正确，故选：D.【点睛】此题考查数轴上数的大小关系，绝对值的性质，有理数的加法法则.20．下列语句正确的是（ ）A ．近似数0．010精确到百分位B ．｜x-y ｜=｜y-x ｜C ．如果两个角互补，那么一个是锐角，一个是钝角D ．若线段AP=BP ，则P 一定是AB 中点【答案】B【解析】【分析】A 中,近似数精确位数是看小数点后最后一位;B 中,相反数的绝对值相等;C 中,互补性质的考查;D 中,点P 若不在直线AB 上则不成立【详解】A 中,小数点最后一位是千分位,故精确到千分位,错误;B 中,x －y 与y －x 互为相反数,相反数的绝对值相等,正确；C 中，若两个角都是直角，也互补，错误；D 中，若点P 不在AB 这条直线上，则不成立，错误故选：B【点睛】概念的考查，此类题型，若能够举出反例来，则这个选项是错误的。

高考物理物理学史知识点易错题汇编附答案解析一、选择题1．许多科学家对物理学的发展做出了巨大贡献，下列选项中说法全部正确的是( )①牛顿发现了万有引力定律，他被誉为第一个“称出”地球质量的人②富兰克林通过油滴实验比较精确地测定了电荷量e的数值③法拉第提出了场的概念并用电场线形象地描述电场④麦克斯韦从理论上预言了电磁波的存在⑤汤姆孙根据α粒子散射实验现象提出了原子的核式结构模型⑥库仑利用扭秤测出了静电力常量k的数值A．①③④ B．②③⑥ C．④⑤⑥ D．③④⑥2．在伽利略的斜面实验中，小球从斜面A上离斜面底端为h高处滚下斜面，通过最低点后继续滚上另一个斜面B，小球最后会在斜面B上某点速度变为零，这点距斜面底端的竖直高度仍为h.在小球运动过程中，下面的叙述正确的是( )①小球在A斜面上运动时，离斜面底端的竖直高度越来越小，小球的运动速度越来越大②小球在A斜面上运动时，动能越来越小，势能越来越大③小球在B斜面上运动时，速度越来越大，离斜面底端的高度越来越小④小球在B斜面上运动时，动能越来越小，势能越来越大A．①② B．②③ C．①④ D．③④3．在物理学发展的过程中，许多物理学家的科学研究推动了人类文明的进程．以下有关物理学史的说法中正确的是 ( )A．伽利略总结并得出了惯性定律B．地心说的代表人物是哥白尼，日心说的代表人物是托勒密C．出色的天文观测家第谷通过观测积累的大量资料，为开普勒的研究及开普勒最终得到行星运动的三大定律提供了坚实的基础Ｄ．英国物理学家牛顿发现了万有引力定律并通过实验的方法测出万有引力常量G的值4．在人类对微观世界的探索中科学实验起到了非常重要的作用。

下列说法符合史实的是A．密立根通过阴极射线在电场和磁场中偏转的实验，发现了阴极射线是由带负电的粒子组成的，并测出了该粒子的比荷B．贝克勒尔通过对天然放射现象的研究，发现了原子中存在原子核C．居里夫妇从沥青铀矿中分离出了钋（Po）和镭（Ra）两种新元素D．卢瑟福通过α粒子散射实验证实了在原子核内部存在质子5．在前人工作的基础上，利用如图所示装置进行定量研究，进而提出两个静止的点电荷之间相互作用规律的物理学家是A．库仑B．安培C．洛伦兹D．奥斯特6．下面说法中正确的是（）A．库仑定律是通过实验总结出来的关于点电荷相互作用力跟它们间的距离和电荷量关系的一条物理规律B．库仑定律适用于点电荷，点电荷就是很小的带电体C．库仑定律和万有引力定律很相似，它们都不是平方反比规律D．当两个点电荷距离趋近于零时，库仑力则趋向无穷7．物理学中最早使用理想实验方法、发现万有引力定律、最早引入了电场概念并提出用电场线表示电场和发现电流磁效应分别由不同的物理学家完成，他们依次是（）A．伽利略、牛顿、法拉第和奥斯特B．牛顿、卡文迪许、洛伦兹和安培C．伽利略、卡文迪许、库仑和奥斯特D．伽利略、牛顿、库仑和洛伦兹.8．了解物理规律的发现过程，学会像科学家那样观察和思考，往往比掌握知识本身更重要。

九年级上册外研版语法知识-英语单项选择100题的易错题汇编附答案含答案一、选择题1．Read this sentence "She felt small as she walked to the enormous, empty stage."Which word has the SAME meaning as the underlined word "enormous"?A．Clean B．Bright. C．Huge D．Tiny2．—Would you like to play King of Glory with me?—Oh, no. That’s the ________ thing in the world I want to do.A．loud B．large C．last D．lost3．It’s really ________ that modern technology can help doctors treat patients online! A．private B．famous C．amazing D．traditional 4．—How do you like the talk show?—I think it's ________, but some people think it's so ________.A．wonderful enough; bored B．enough wonderful; boringC．wonderful enough; boring D．enough wonderful; bored5．The Spring Festival is one of the ______ festivals in China and everyone loves to celebrate it. A．modern B．traditional C．international D．ancient6．There isn’t an airport near where I live. The _______ one is about 90 miles away. A．busiest B．farthest C．newest D．nearest7．It’s _________ knowledge that bad moods can have an in fluence on our health.A．unusual B．special C．general D．common8．As the number of the novel coronavirus infections grows___________, the World Heath Organization takes active steps to control the serious disease.A．more B．larger C．higher D．wider9．—Do you know about the story of the Little Horse Crossing the River?—Yes, at last the little horse finishes crossing the river and he knows how ________the river is. A．wide B．long C．deep D．clear10．—Jack is such a ________ person that everyone likes him.—He is. He always offers a hand when his neighbours are in trouble.A．curious B．confident C．helpful D．serious11．My little sister is ________ and she always asks me different kinds of strange questions. A．creative B．wise C．curious D．generous 12．—How do you feel about the dish?—Look! This is nothing but ________ vegetable soup.A．famous B．wonderful C．unusual D．common13．I hear there will be ________jobs for people because robots will do some of the jobs. A．fewer B．less C．more D．better14．I think “heroes in harm’s wa y(逆行者)” must be one of the ________words on the Internet last year.A．hottest B．widest C．cleverest D．driest15．I'm always ____________ before the exam. I often try to make myself calm down by taking adeep breath.A．relaxed B．bored C．nervous D．happy 16．—Have you unlocked any new skills during the long winter holiday?—Yes. Cooking has become more and more ____ and I can cook nice dishes now. A．comfortable B．difficult C．different D．popular 17．— What do you think of those doctors in Wuhan, Ma Lin?—How brave they are! They’ve tried their best to keep patients ________.A．live B．alive C．living D．lively18．— Are you going to take part in the speech competition?—That’s for sure. It’s _______ a chance to miss.A．small enough B．good enough C．too small D．too good 19．—What do you think of his ___________ play?—I like it much better than his ___________one.A．latest; last B．last; laster C．last; last D．latest; latest 20．Many companies try to get into the market by offering _______ rewards to their customers. A．peaceful B．primary C．generous D．general 21．—Dad, I've tried my best but I still can't solve these problems.—Don't worry, my son. No one is ________ and everyone fails from time to time. A．successful B．confident C．perfect D．excellent 22．— Sorry, I can't afford to go abroad.— What about having a country travel with a little________ price?A．cheaper B．higher C．lower D．less23．Mr Zheng is so ______that he has donated five million yuan to the schools in his hometown. A．energetic B．patient C．humorous D．generous 24．— It will be a long time before Mike finishes doing his homework.— Yeah, you have to be________with our kid.A．strict B．popular C．serious D．patient 25．—Sorry, I don't know how many colours there are in a rainbow.—Are you joking? This is just ________ knowledge.A．natural B．general C．proper D．ancient 26．With true friends, we feel ________ to share our joy and sadness to the greatest possible degree.A．free B．suitable C．strange D．friendly 27．—We’re late! It’s already 7:30.—Don’t worry. My clock is 20 minutes ________.A．fast B．late C．slow D．early28．It’s ________ knowledge that moods can have an influence on our health.A．unusual B．special C．general D．common 29．—Peter, have you heard of the song Let it go?—Yes, it sounds _________ and it's popular among young people.A．nice B．bad C．terrible D．strange30．Although this may sound like a ________ process, great care is needed.A．stupid B．similar C．simple D．strict31．—How was your exam the day before yesterday?—Well, I feel quite good. I made ________ mistakes than before.A．fewer B．the fewest C．less D．the least 32．—Linda is practising the violin for an hour these days.—I see. It’ll make her ________ enough to perform on stage tonight.A．active B．humorous C．confident D．patient33．The girl’s voice sounds ________. Maybe she can become a good singer when she grows up. A．terrible B．well C．sweet D．wonderfully 34．Mr. King is very ________. He explains the difficulties many times until we understand them. A．strict B．patient C．polite D．hard-working 35．You’ve watched the boring soap opera thousands of times! Why don’t you go outside and find something ________ doing?A．useful B．cheerful C．enjoyable D．worth36．—You haven’t said a ________ word since last Friday. What’s wrong?—Nothing. Just let me alone.A．simple B．single C．similar D．silent37．You may meet many difficulties in the future, you should learn to be ________ enough to take on any challenge.A．confident B．modest C．generous D．curious 38．—Like so many creative people, he was never ________.—That’s why he has made lots of valuable paintings.A．cheerful B．skillful C．satisfied D．surprised 39．Yesterday’s film was really ________ and it made all of us laugh.A．boring B．funny C．meaningless D．expensive 40．—Have you found that more and more visitors come to our hometown?—You’re right. That’s because we’re now building Huai’an a ________ city！A．live B．lively C．living D．alive41．Our monitor Jenny is so ________ that she always keeps things in good order. A．organized B．practical C．generous D．modest42．This is the chance he needs to make a ________ start.A．curious B．patient C．fresh D．natural 43．—Mr. Green, please feel ________ to let us know if you aren’t satisfied with our service.— OK, I will. It has been good so far.A．real B．ready C．free D．fresh44．David promised to help me with my physics last Sunday. But to my great disappointment, he never appeared that day.What does the word “disappointment” mean in the sentence?A．The feeling of being nervousB．The feeling of being lonelyC．The feeling of being unhappyD．The feeling of being worried45．It is ________ for people to drive after drinking or without wearing a seat belt.A．sick B．dangerous C．funny D．important 46．— Mary can get good marks in all her subjects, but she never shows off.— I agree. She is ________.A．generous B．modest C．patient D．curious47．—It will be ________.—That’s great! The whole world will be white.A．sunny B．cloudy C．snowy D．foggy48．This kind of drink tastes ________ but there’s only ________ in this bottle. I’d like some more.A．good；a little B．well；a little C．good；little D．well；little 49．— More and more people like group buying on WeChat.— You said it. The prices are ________.A．much lower B．much cheaper C．more expensive D．even higher 50．In the USA, many people use decorations to make their yards more ________.A．live B．lively C．alive D．living二、选择题51．My family is always ___________ me no matter what I decide to do. That makes me very pleased.A．above B．behind C．against D．through52．My mum searched ________ the messy books and found my pencil was under a Harry Potter. A．as B．across C．through D．for53．The blue planet is so far from the earth that radio signals, travel ________ the speed of light, take 16 hours to reach the spacecraft.A．for B．in C．on D．at54．—I can’t think of any other actress who is more beautiful than Audrey Hepburn.—You’ve got the point. Her beauty is ________ words and she succeeded ________ hard work. A．over; by B．over; throughC．beyond; by D．beyond; through55．Everyone was touched ________ words after they watched the film Hi, MOM 《你好，李焕英》directed by Jia Ling.A．under B．across C．beyond D．against56．—I want to visit Liaoning History Museum. Is it open today?—No. It opens every day ________ Monday.A．except B．till C．between D．after 57．—When is your birthday?—My birthday is ________ August 21st.A．on B．at C．in D．for58．The chopsticks are ________ wood.A．made of B．made from C．made in D．made with 59．The girl is ________ a singer ________ everyone in her hometown.A．well known as; for B．well-know as; toC．well known as; to D．best known for; for60．The workers will build a new road ________ the two villages.A．from B．among C．at D．between61．My family get together and have a big dinner ________ Sundays.A．at B．in C．on D．to62．The teacher encouraged the students to tell the story ________ English.A．at B．with C．in D．for63．— Would you like to visit the zoo with me now?—Sorry, it’s _______ the visiting hours. Let’s go there tomorrow.A．beyond B．through C．during D．on64．The story The Ugly Duckling ________ Hans Christian Andersen has remained popular among children for centuries.A．in B．on C．by D．with65．In the end， Mr Song came up____a good method to solve the problem．A．for B．at C．in D．with66．Peter is clever enough to read and write __________ the age of 4.A．between B．at C．to D．during 67．Switzerland lies ________ France, Germany, Austria and Italy.A．between B．among C．against D．beyond 68．Family is always _________ me, so I can follow my dreams with great courage. A．beyond B．forward C．past D．behind69．— What do you think of those smart kids in the game show?— There is no doubt that many of them have a gift ________ maths.A．for B．in C．on D．at70．—There have been great changes in Taizhou in the past few years.—I can't agree more. The changes there are ________ my imagination.A．near B．past C．along D．beyond 71．Though there are so many things around us that go ______ our will, we can’t give up because following the dream is valuable.A．through B．towards C．against D．beyond72．You shouldn’t eat so much chocolate _________ meals. Because it wi ll affect your appetite. A．except B．through C．between D．unless73．— Excuse me, will you please tell me the way to Yangzhou State Guesthouse?— Walk ______ the bridge and go straight on, and you will see it on your left.A．over B．above C．across D．into74．—How can I improve my English more quickly, Tom?—__________listening and reading more.A．At B．Across C．By D．On75．________ a spring morning, a bird flew into our classroom and we were very excited to see it. A．In B．On C．At D．For 76．Sometimes I feel stressed because what my parents want me to do has gone ________ my ability.A．through B．against C．above D．beyond 77．Don’t be afraid of difficulties. Remember: kites rise highest ________ the wind, not with it. A．over B．against C．across D．along78．— When will Mr. Smith arrive?— ________ September 6th.A．At B．In C．On D．For79．—We must study hard to enter our ideal high school.—Exactly! Just as President Xi says,“Happiness is achieved ________ hard work.”A．through B．across C．along D．with80．The little stream ran dawn from a high mountain ________ many villages and forests. A．across B．against C．beyond D．through 81．—The earthquake in Ya’an took place ________ two past eight ________ the morning of April 20th.—Yes, some people were still sleeping for it was weekend.A．in; on B．on; in C．at; in D．at; on82．There is a stone bridge ________ the river in front of my house.A．over B．under C．above D．below83．The 20th China Jiangning Hengxi Watermelon Festival was held ________ May this year. A．at B．on C．in D．from84．In west ern countries, children play “trick or treat” ________ the evening of October 31st. A．at B．in C．on D．to85．The underground in this city has been ________ service for almost 3 years.A．on B．in C．at D．of86．________small actions, like reusing water, we can make a great difference to our world. A．Across B．Beyond C．Through D．Against 87．Anyone who can find the clues ________ the case will get a reward of 5,000 yuan.A．with B．to C．at D．from88．A study shows that rude languages spoken to children may have bad results that go ________ those of beating them.A．against B．beyond C．except D．with89．Let’s vote ________ China’s Inspirational Role Models(感动中国人物) ________ the Internet, shall we?A．for; in B．to; on C．on; over D．for; on90．I like reading. I often fill my bookshelf ________ all kinds of books, like novels, detectivestories, and so on.A．on B．in C．with D．of91．Don’t be afraid of difficulties. Remember: kites rise highest ________ the wind, not with it. A．against B．above C．across D．along92．Some of the technolog y we’ve seen on screen is ________ our ability to create. But that might not be true for long.A．against B．during C．beyond D．through93．A new bridge the Yangtze River in Nanjing opened to traffic on Dec. 24, 2020. A．through B．over C．on D．along94．— Maybe you should call her up.—But I don’t want to talk with her ________ the phone.A．at B．in C．on D．with95．She was forced to marry ________ her mind to receive the following painful life. A．against B．with C．by D．in96．—It’s raining heavily ou tside. May I push my bicycle into your house?—Certainly. But please put it _________ the wall so that it won’t take up too much space.A．in B．on C．against D．over97．It is believed that ________ December 21, 1891, the first basketball game in history was played.A．in B．on C．at D．for98．—Why can’t we drive in the emergency lane (应急车道) on expressway?—Because the lane makes it possible to race ________ the clock to save people’s lives. A．beyond B．over C．against D．through 99．New York City, also known ________ Big Apple, becomes one of the world’s greatest business and cultural centers.A．as B．by C．for D．to100．—How did you get to the zoo, Helen?—I went to the bus station ________ my bike, and took the No. l bus to the zoo.A．on B．by C．in D．with【参考答案】***试卷处理标记，请不要删除一、选择题1．C解析：C【详解】题意：读这句话“当她走向巨大的空空的舞台时，她感觉很渺小。

初中英语单选易错题精编1．Which do you enjoy _____your spare time, playing cards at home or taking a walk in the park?A. spendingB. to spendC. having spentD. to have spent解析：同学们对于enjoy后接-ing动词记得很熟，已成思维定势，所以会不假思索地选A，而实际上此句enjoy 的宾语是which，空白处应填入一个不定式，表目的，整句话的意思是“你喜欢做什么来度过你的空闲时间，在家玩牌还是去公园散步？”故正确选项应为B。

另外，通过这道题我们还可以学到一个短语，spare time——空闲时间、闲暇时间，这里spare作形容词，表示“空闲的，多余的”。

free time也可以表示“空闲时间”。

2．I’m sorry I cannot help _____ the work.A. to finishB. finishingC. finishedD. to finishing解析：一些学生由于受cannot help doing sth.(禁不住做某事)这一习惯用法的影响，毫不犹豫地选择了B。

然而，只要仔细分析一下句子，根据句意，“对不起，我不能帮忙完成这项工作。

”就可知道正确答案为A。

cannot help to do sth.表示“不能帮助做某事”，这时，help后的不定式可带to也可不带to。

所以，同学们，当题中见到can't help的时候不要想当然的选doing形式哦，一定要根据句意来分析一下。

3．—Would you like some tea，please？—Yes. I prefer tea _____ sugar.A. toB. forC. withD. of解析：大家易受固定搭配prefer...to...（喜欢......而不喜欢......）的影响而错选A。

初三政治选择题易错题及难题精选48道1、习近平的出访，从严寒的俄罗斯到火热的非洲大陆，涉及大国、发展中国家、周边多边关系，涵盖政治、经济、文化安全等领域，并出席了金砖国家领导人会晤。

此次外交活动传递的信息是：从整整三本练习册、各类试卷及中考真题中挑选，作为期末复习、中考复习都非常有效果。

a中国继续高举和平、发展、合作、共赢的旗帜b大国关系和经济贸易仍然是中国外交的核心内容c中国经济应对经济全球化和世界多极化的深入发展d中国仍然坚持自己作为世界上最大发展中国家的定位A abcB abdC bcdD acd2、2011年11月29日，政府宣布大幅上调国家扶贫标准线。

这说明：A新中国成立后，中国人民富起来了，国家强了起来B这个从20世纪50年代进入社会主义初级阶段，国际地位显著提高C十一届三中全会以来人民得到的实惠越来越多D改革开放式强国之路3、统计数据显示：截止2013年初，新一轮援疆已累计实施援助新疆地方项目2378个，拨付到位援助资金达248亿元，其中75%以上资金都用于民生建设。

这：A说明少数民族离不开汉族B表明民族区域自治是我国的一项基本国策C有利于实现各民族的同步发展D有利于各民族相互团结、共同发展、共同繁荣4、2014年某市在教育领域的投入，不仅数巨大，而且具有强烈的人文精神。

如为在园孤儿、残疾幼儿、家庭困难幼儿发放保育费补贴；为农村义务教育阶段学生发放营养餐补助；为城市义务教育在校生免除课本费、作业本费等等。

这体现了：a该市重视教育发展，把教育放在游戏发展的战略位置b关注民生问题，体现了以人为本的理念c科技发展依靠教育d只有加大财政投入，才能解决教育难题A abB cdC adD bd5、据国家电力部门消息，今后普通用户不但能用太阳能、风能等新能源发电装置给自己家供电，还可以讲用不完的电卖给国家电网。

这种新举措：a有利于保护生态环境b有利于缓解资源压力c符合可持续发展战略d有利于加强国有经济地位A abcB abdC acdD bcd6、“物价上涨慢一点，收入增长快一点，就业机会多一点，资源消耗少一点，孩子学费降一点，医疗费用低一点------”这一民谣从根本上反映了：A经济发展与人口发展之间的矛盾 B 现阶段我国社会的主要矛盾C东部地区与西部地区发展部平衡 D 我国人民生活水平还不够高7、当得十八大指出：30年来，我国的快速发展史改革开放推动的，未来中国的发展，也必须继续深入推进改革开放。

高考单选易错题、难题、好题题型专项辅导(附答案)(word版可编辑修改) 编辑整理：尊敬的读者朋友们：这里是精品文档编辑中心，本文档内容是由我和我的同事精心编辑整理后发布的，发布之前我们对文中内容进行仔细校对，但是难免会有疏漏的地方，但是任然希望（高考单选易错题、难题、好题题型专项辅导(附答案)(word版可编辑修改)）的内容能够给您的工作和学习带来便利。

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高考单选易错题、难题、好题题型专项辅导（附答案）1。

By the time you arrive in London， we _____ in Europe for two weeks。

A. shall stayB. have stayed C。

will have stayed D. have been staying2. I appreciated ____ the opportunity to study abroad two years ago.A。

having been given B. having given C. to have been given D. to have given3. Living in the central Australian desert has its problems， _____ obtaining water is not the least。

A。

of which B. for what C. as D。

whose4. The heart is ____ intelligent than the stomach， for they are both controlled by the brain.A. not so B。

1.机动车登记证书、号牌、行驶证灭失、丢失或者损毁的，机动车所有人应当向哪个部门申请补领、换领。

A、当地公安局B、住地交警支队车辆管理所C、登记地车辆管理所D、驾驶证核发地车辆管理所答案：C登记证书、号牌、行驶证是车辆信息，申领的时候在登记地车辆管理所，补办的时候当然也在登记地车辆管理所。

2.申请人以欺骗、贿赂等不正当手段取得机动车驾驶证的（被撤销的），申请人在多长时间内不得再次申领机动车驾驶证。

A、3年B、1年C、2年D、6个月答案：A《公安部令第123号》第七十八条：申请人以欺骗、贿赂等不正当手段取得机动车驾驶证的，公安机关交通管理部门收缴机动车驾驶证，撤销机动车驾驶许可；申请人在三年内不得再次申领机动车驾驶证。

3.驾驶机动车跨越双实线行驶属于什么行为？A、违规行为B、过失行为C、违法行为D、违章行为答案：C驾驶机动车跨越双实线行驶是违反《交通安全法》的行为，是违法行为。

4.驾驶人违反交通运输管理法规发生重大事故致人重伤、死亡，可能会受到什么刑罚？A、处5年以上徒刑B、处3年以上7年以下徒刑C、处7年以上徒刑D、处3年以下徒刑或者拘役答案：D《中华人民共和国刑法》第一百三十三条：违反交通运输管理法规，因而发生重大事故，致人重伤、死亡或者使公私财产遭受重大损失的，处三年以下有期徒刑或者拘役；交通运输肇事后逃逸或者有其他特别恶劣情节的，处三年以上七年以下有期徒刑；因逃逸致人死亡的，处七年以上有期徒刑。

题中只说了“违反交通运输管理法规发生重大事故致人重伤、死亡”，并无其他情节，所以是【处3年以下徒刑或者拘役】。

5.驾驶人违反交通运输管理法规发生重大事故使公私财产遭受重大损失，可能会受到什么刑罚？A、处5年以上徒刑B、处3年以上7年以下徒刑C、处3年以上徒刑D、处3年以下徒刑或者拘役答案：D《中华人民共和国刑法》第一百三十三条：违反交通运输管理法规，因而发生重大事故，致人重伤、死亡或者使公私财产遭受重大损失的，处三年以下有期徒刑或者拘役；交通运输肇事后逃逸或者有其他特别恶劣情节的，处三年以上七年以下有期徒刑；因逃逸致人死亡的，处七年以上有期徒刑。

中考英语单选题100道易错题合集含答案详解1. —Do you know what he did all day?—He spent as much time playing as he ______.A. studyingB. was studyingC. studiedD. did studying2. I can’t say ______I want to see him again. We haven’t seen each other for a long time.A. how longB. how soonC. how oftenD. how much3. It is said that land animals ______ from sea animals.A. were developedB. developedC. are developingD. develops4. —Would you like some coffee?—Yes, and please get me some milk, too. I prefer coffee ______milk.A. toB. withC. thanD. of5. ______ made his teacher unhappy.A. Tom came lateB. Tom’s came lateC. Tom’s lateD. Tom’s coming late6. Father asked Edison ________.A. what was he doing that forB. why he was doing that forC. how he was doing that forD. what he was doing that for7. We are going to have the sports meeting _____it _______tomorrow.A. if, rainsB. unless, will rainC. unless, rainsD. when, will rain8. ______ of the students in our class _______ from the country.A. Three fifth, isB. Three fifths, areC. Third fives, areD. Three five, is9. News can _____every corner of the world with the help of the Internet.A. reachB. arriveC. getD. reach to10. Here is only one seat for the old man________.A. to sitB. sittingC. sitting onD. to sit on11. Though this pair of shoes is a bit expensive, I would like to________.A. try them onB. try on themC. try them outD. try out them12. How can we finish ____ much work in ___a short time?A. so, soB. such, suchC. so, suchD. such, so13. Last night, he had his car________.A. to stealB. stoleC. stealingD. stolen14. Last night several young men ________the bank of lots of money.B. robbedC. tookD. got15. Where was this big egg_____?A. liedB. lainC. laidD. lay16. _______ school, we can get much knowledge.A. BecauseB. Thanks forC. Thanks withD. Thanks to17. You’d better think about ________ a car now.A. whether buyB. if buyC. whether to buyD. if to buy18. He talks too much as if he ______everything.A. knowsB. knewC. has knownD. to know19. He will come to stay with us for _________________ next month.A. some time sometimeB. sometime some timeC. sometimeD. some times20. This radio program is well worth________.A. listeningB. listening toC. watchingD. to listen21. He must be a doctor, _________?A. mustn’t heB. must heD. isn’t he22. This building is taller than _________one around it.A. any otherB. another oneC. anyD. some other23. Though he live________, he doesn’t feel ________ because he can enjoy himself at home.A. lonely, lonelyB. alone, aloneC. alone, lonelyD. lonely, alone24. Yangzhou High School sounds _________ a good one. But I would like to have more information about it.A. /B. asC. likeD. what25. —How long_______ you _______ the English dictionary?—About half a year.A. have, gotB. did, buyC. have, hadD. have, bought26. _______ my great surprise, such a little boy can draw so many beautiful pictures.A. InB. WithC. ToD. For27. _____the old man spoke, ____he became.A. The more, the angryB. The more, the more angrilyC. The more, the angrierD. The most ,the angrier28. ____the help of my English teacher, I did well in English last term.A. UnderC. WithD. For29. She _____a teacher, but now she is a doctor.A. used beB. used to beC. was used to beD. was30. What do you think __________him change his mind?A. to makeB. madeC. makeD. making31. They are practising _______in the hall.A. danceB. to danceC. dancingD. to dancing32. It is _____that we all like to read it.A. so good a book.B. such good a bookC. so a good bookD. such good books33. She often offers _______.A. us with some foodB. some food to usC. us to some foodD. money me34. Most sharks feed _____ fish and other animals.A. withB. forC. onD. by35. —Can you look after my daughter for me while I am away? —______.A. It’s a pleasureB. With pleasureC. Not at allD. You’re welcome36. Can you think of a way ________ it？A. doingB. doC. to doD. of do37. I’ll get her _______harder. You wait and see.A. studyB. to studyC. studiedD. studies38. Hearing his mother’s voice, the child couldn’t wait _______out.A. rushingB. to rushC. rushedD. for rushing39. The king _______himself from a leaning tree.A. hungB. hangedC. hungedD. hang40. Jim got up early _______ he caught the early train.A. becauseB. orC. so thatD. until41. When _______the PRC______, do you know?A. did, findB. did, foundC. was, foundD. was, founded42. What’s six _________ seven?A. multipliesB. multiplyingC. multipliedD. multiplied by43. My watch has stopped. It seems that I’ll go and _____ this afternoon.A. have someone repaired itB. have someone to repair itC. have someone repair itD. have it repair44. I’m sure that their team will ______ ours.A. failB. takeC. winD. beat45. The flight was put off ________ fog.A. becauseB. as the resultC. as a result ofD. as46. He watched the game with a ______look.A. surprisingB. surprisedC. surpriseD. surprises47. _____the time he got up, the road had already been covered with think snow.A. ForB. ByC. AtD. Until48. It’s very ________ to talk with him.A. worthB. rewardingC. deserveD. pleasure49. To help animals is _______humans themselves.A. helpB. helpingC. helpfulD. to helping【注意：帮助动物就是帮助人类自己有以下4种翻译】①To help animals is to help humans themselves.② Helping animals is helping humans themselves.③To help animals is helping humans themselves.④ H elping animals is to help humans themselves.牢记：动名词实质上是名词，在句子中做主语、宾语、表语。

2021年中考冲刺易错题答案（含解析）一、单选题1、如图，在▱ABCD中，将△ADC沿AC折叠后，点D恰好落在DC的延长线上的点E处．若∠B＝60°，AB＝3，则△ADE的周长为（）A．12 B．15 C．18 D．21【分析】依据平行四边形的性质以及折叠的性质，即可得到BC＝2AB＝6，AD＝6，再根据△ADE是等边三角形，即可得到△ADE的周长为6×3＝18．【解答】解：由折叠可得，∠ACD＝∠ACE＝90°，∴∠BAC＝90°，又∵∠B＝60°，∴∠ACB＝30°，∴BC＝2AB＝6，∴AD＝6，由折叠可得，∠E＝∠D＝∠B＝60°，∴∠DAE＝60°，∴△ADE是等边三角形，∴△ADE的周长为6×3＝18，故选：C．【点评】本题考查了平行四边形的性质、轴对称图形性质以及等边三角形的判定．解题时注意折叠是一种对称变换，它属于轴对称，折叠前后图形的形状和大小不变，位置变化，对应边和对应角相等．2、下列图形中，一定既是轴对称图形又是中心对称图形的是（）A．等边三角形B．直角三角形C．平行四边形D．正方形【分析】根据轴对称图形和中心对称图形的概念对各选项分析判断即可得解．【解答】解：A、等边三角形是轴对称图形，不是中心对称图形，故本选项错误；B、直角三角形不是轴对称图形，也不是中心对称图形，故本选项错误；C、平行四边形不是轴对称图形，是中心对称图形，故本选项错误；D、正方形既是轴对称图形，又是中心对称图形，故此选项正确．故选：D．【点评】本题考查了中心对称图形与轴对称图形的概念．轴对称图形的关键是寻找对称轴，图形两部分折叠后可重合，中心对称图形是要寻找对称中心，旋转180度后两部分重合。

3、下列四个银行标志中，既是中心对称图形，又是轴对称图形的是（）A．B．C．D．【分析】根据轴对称图形和中心对称图形的概念对各选项分析判断即可得解．【解答】解：A、是轴对称图形，不是中心对称图形，故本选项错误；B、是轴对称图形，不是中心对称图形，故本选项错误；C、既是轴对称图形，也是中心对称图形，故本选项正确；D、是轴对称图形，不是中心对称图形，故本选项错误．故选：C．【点评】本题考查了中心对称图形与轴对称图形的概念．轴对称图形的关键是寻找对称轴，图形两部分折叠后可重合，中心对称图形是要寻找对称中心，旋转180度后两部分重合.4、2019年6月6日，南宁市地铁3号线举行通车仪式，预计地铁3号线开通后日均客流量为700000人次，其中数据700000用科学记数法表示为（）A．70×104B．7×105C．7×106D．0.7×106【分析】根据科学记数法的表示方法a×10n（1≤a＜9），即可求解；【解答】解：700000＝7×105；故选：B．【点评】本题考查科学记数法；熟练掌握科学记数法的表示方法是解题的关键．5、下列四个图案中，是中心对称图形的是（）A．B．C．D．【分析】根据中心对称图形的概念对各选项分析判断即可得解．【解答】解：A．此图案是中心对称图形，符合题意；B．此图案不是中心对称图形，不合题意；C．此图案不是中心对称图形，不合题意；D．此图案不是中心对称图形，不合题意；故选：A．【点评】本题考查了中心对称图形的概念，中心对称图形是要寻找对称中心，旋转180度后两部分重合．6、关于x的一元二次方程x2﹣（k﹣1）x﹣k+2＝0有两个实数根x1，x2，若（x1﹣x2+2）（x1﹣x2﹣2）+2x1x2＝﹣3，则k的值（）A．0或2 B．﹣2或2 C．﹣2 D．2【分析】由根与系数的关系可得出x1+x2＝k﹣1，x1x2＝﹣k+2，结合（x1﹣x2+2）（x1﹣x2﹣2）+2x1x2＝﹣3可求出k的值，根据方程的系数结合根的判别式△≥0可得出关于k的一元二次不等式，解之即可得出k的取值范围，进而可确定k的值，此题得解．【解答】解：∵关于x的一元二次方程x2﹣（k﹣1）x﹣k+2＝0的两个实数根为x1，x2，∴x1+x2＝k﹣1，x1x2＝﹣k+2．∵（x1﹣x2+2）（x1﹣x2﹣2）+2x1x2＝﹣3，即（x1+x2）2﹣2x1x2﹣4＝﹣3，∴（k﹣1）2+2k﹣4﹣4＝﹣3，解得：k＝±2．∵关于x的一元二次方程x2﹣（k﹣1）x﹣k+2＝0有实数根，∴△＝[﹣（k﹣1）]2﹣4×1×（﹣k+2）≥0，解得：k≥2﹣1或k≤﹣2﹣1，∴k＝2．故选：D．【点评】本题考查了根的判别式以及根与系数的关系，利用根与系数的关系结合（x1﹣x2+2）（x1﹣x2﹣2）+2x1x2＝﹣3，求出k的值是解题的关键．7、下列运算正确的是（）A．a•a2＝a2B．5a•5b＝5ab C．a5÷a3＝a2D．2a+3b＝5ab【分析】直接利用单项式乘以单项式以及同底数幂的乘除运算法则、合并同类项法则分别化简得出答案．【解答】解：A、a•a2＝a3，故此选项错误；B、5a•5b＝25ab，故此选项错误；C、a5÷a3＝a2，正确；D、2a+3b，无法计算，故此选项错误．【点评】此题主要考查了单项式乘以单项式以及同底数幂的乘除运算、合并同类项，正确掌握相关运算法则是解题关键．8、如图，从点C观测点D的仰角是（）A．∠DAB B．∠DCE C．∠DCA D．∠ADC【分析】根据仰角的定义进行解答便可．【解答】解：∵从点C观测点D的视线是CD，水平线是CE，∴从点C观测点D的仰角是∠DCE，故选：B．【点评】本题主要考查了仰角的识别，熟记仰角的定义是解题的关键．仰角是向上看的视线与水平线的夹角；俯角是向下看的视线与水平线的夹角．9、下列图形中，一定既是轴对称图形又是中心对称图形的是（）A．等边三角形B．直角三角形C．平行四边形D．正方形【分析】根据轴对称图形和中心对称图形的概念对各选项分析判断即可得解．【解答】解：A、等边三角形是轴对称图形，不是中心对称图形，故本选项错误；B、直角三角形不是轴对称图形，也不是中心对称图形，故本选项错误；C、平行四边形不是轴对称图形，是中心对称图形，故本选项错误；D、正方形既是轴对称图形，又是中心对称图形，故此选项正确．故选：D．【点评】本题考查了中心对称图形与轴对称图形的概念．轴对称图形的关键是寻找对称轴，图形两部分折叠后可重合，中心对称图形是要寻找对称中心，旋转180度后两部分重合。