语法点拨：if与unless引导的条件状语从句
1．常用引导词：if（如果），unless（除非）。
I won’t go to the movies unless I am free tomorrow.
除非我明天有空，否则我不会去看电影。
2．条件状语从句的位置
可放在句首或句尾，放在句首时常用逗号与主句隔开。
e.g.If it rains tomorrow, I will stay at home.
= I will stay at home if it rains tomorrow.
如果明天下雨我就呆在家里。
3．if引导词用法
if引导的条件句有：真实条件句和非真实条件句两种。
真实条件句：表示在某种条件下某事很可能发生。
e.g.If you ask him, he will help you.
如果你请他帮忙，他会帮你的。
4．unless引导词用法
固定搭配：unless=if...not 除非，若不，如果不
e.g.You will fail to arrive there in time unless
you start earlier.
=If you don’t start earlier, you will fail to
arrive there in time.
如果你不早点动身，你就不能及时赶到
那儿。
注意：在含有条件状语从句的复合句中，当主句是一
般将来时态，从句要用一般现在时（即主将从现原
则）。如果主句是祈使句或含有情态动词时，从句也
用一般现在时表将来。
e.g.If you study hard, you will pass the exam.
1.I will send you an e-mail as soon as I____A___in Canada.
A.arrive
B.arrived
C.am arriving
D.will arrive
2.If there____A___no buying and selling of animals,there______no killing in nature.
A.is;will be
B.will be;will be
C.is;is
D.will be;is
3.I’m waiting for my friend.__C___,I'll go shopping alone.
A.If she comes
B.If she won't come
C.If she doesn't come
5.You can’t watch TV___A_____you finish your homework.
A.unless
B.if
C.while
D.as
7.The students_____A___have a sports meeting this weekend if it__ _.
A.won’t;rains
B.will;rains
C.won’t;will rain
D.are going to;is going to rain
9.I don't know if she____B___to my birthday party tomorrow.If she ______,I'll be very happy.
es;comes
B.will come;comes
es;will come
10.—When will you come to Daqing?—I will call you___D__I arrive.
A.till
B.while
C.as quickly as
D.as soon as
11.I’ll give it to Jim as soon as I___C____him tomorrow.
A.saw
B.will see
C.see
D.have seen
