第二部分阅 读

　　第一节短文理解

　　阅读下列短文，从每题所给的A.、B.、C.、D.四个选项中，选出最佳选项，并在答题卡上将该项涂黑。

　　Text 1

　　It’s a time when school，homework，active social lives and part-time jobs kc印teenagers(青少年)busy from early in the morning until late at night.They are likely to try to make up for a lack of sleep by“sleeping in”on the weekends.Unfortunately.this causes irregular sleep and ac-tually makes the problem worse.

　　Most teenagers are not able to fall asleep until late at night.Since many teens aren’t sleepy until around ll P.m.，but need to be at school by 7：300r 8：00 a.m.，they cannot get enough sleep.During puberty(青春期)，the biological clock in the brain naturally re.sets to a later time，and this causes teens to fall asleep later.Then，when it’s time to get up，a teen’s body clock is likely to still be producing the night-time hormones(荷尔蒙).This makes it hard for them to feelactive and energetic in the morning.

　　A growing body of research suggests that starting high school later improves aRendance，achievements and grades.A few years ago in an important study，test scores on the SAT college entrance exams in Edina，Minnesota jumped more than l00 points on average，when the morning school bell rang an hour later.Unfortunately，most schools are not set up to start later and fail to satisfy teen’s sleep needs.

　　21.What effect does“sleeping in”on the weekends have on teenagers?

　　A.Improving their health.

　　B.Weakening their energy.

　　C.Disturbing their biological clock.

　　D.Making up for their hormone loss.

　　22.The study in Minnesota shows that starting moming school one hour later helps to__________.

　　A.make teenagers grow faster

　　B.change teenagers’sleep needs

　　C.do more research on teenagers

　　D.improve students’achievements

　　23.The text helps US to know more about teenagers’__________.

　　A.daytime activities

　　B.sleeping habits

　　C.mental problems

　　D.studying methods