阅读理解
Students who rely on working at night to improve their grades might want to sleep on that strategy：A new survey in the US says those who never study all night have slightly higher grades than those who do.
A survey of 120 students at St. Lawrence University found that students who had never pulled an allnighter on average had higher grades than those who had.The survey found those who did not study through the night had a grade point average of 3.2 compared to 2.95 for those who did. The study，by assistant professor of psychology Pamela Thacher，is to be included in the January issue of Behavioral Sleep Medicine.
“It’s not a big difference，but it’s pretty striking，”Thacher said, “I am primarily a sleep researcher and I know nobody thinks clearly at 4∶00 in the morning.You think you can do，but you can’t.”
Many college students，of course，have inadequate or irregular sleep，for reasons ranging from excessive caffeine to poor time management.
“A lot of students were under the impression that all-nighters were a very useful tool for accomplishing work，and that caffeine intake was very useful in meeting deadlines and stuff like that，” said Mr Chatani，who had a 3.4 grade point
average last term.
Dr Howard Weiss，a physician at St. Peter’s Sleep Center in Albany，said the study results made sense. “Certainly that data is out there showing that short sleep duration absolutely interferes with concentration and performance on objective testing，” he said.
“Some night owls do get good grades，of course，which may be explained by circadian(昼夜节律的，生理节奏的)rhythms，” Weiss said, “Some people have different 24hour body clocks from others，and may do better depending on classes and testing time.”
1.The purpose of the passage is to tell us ________.
A.the bad effects of pulling an allnighter
B.pulling an allnighter leads to sleep problems
C.Thacher’s doubt about all nighters
D.all nighters influence students’ grades
2.According to Thacher’s study，around 4 o’clock i n the morning is a time when _________.
A.one can think more clearly
B.one has his/her best memory
C.one can’t learn efficiently
D.one’s brain falls into a period of deep sleep
3.What can we know from Dr Howard Weiss’s words？
A.Thacher’s study is not convincing enough.
B.He believes in Thacher’s study.
C.Thacher’s study makes no sense.
D.Thacher should take exceptions into consideration.
4.An allnighter in the passage refers to _____________.
A.a habit of accomplishing work by skipping a whole night’s sleep
B.a drink to keep people awake all night
C.a person who falls into the habit of working at night
D.a way to improve one’s grade by working deep into the night
学海浪花：
1.strategy n．策略，计谋[U]
2.primarily adv.最初，基本，根本，初步
3.inadequate adj.不适当的，不充分的，不能胜任的[反]adequate；adv.adequately；n.adequateness；adequacy
4.intake n．吸收(量)，纳入(量)，the yearly intake of students每年的招生量
5.duration n．耐久，持久，(持续)期间
学海导航：本文是一篇说明文。调查表明，那些从来不熬夜的学生的学习成绩往往要比那些常常熬夜的学生的学习成绩优秀。熬夜往往不能保证学生有足够的精力，对第二天的学习活动会有很大的负面影响。
1. D解析：目的判断题。根据第一段中的“those who never
