Getting less sleep has become a bad habit for most American kids.According to a new survey(调查) by the National Sleep Foundation,51% of kids aged 10 to 18 go to bed at 10 pm or later on school nights,even though they have to get up early.Last year the Foundation reported that nearly 60% of 7-to 12-year-olds said they felt tired during the day,and 15% said they had fallen asleep at school.

　　How much sleep you need depends a lot on your age.Babies need a lot of rest:most of them sleep about 18 hours a day!Adults need about eight hours.For most school-age children,ten hours is ideal(理想的).But the new National Sleep Foundation survey found that 35% of 10-to 12-year-olds get only seven or eight hours.And guess what almost half of the surveyed kids said they do before bedtime?Watch TV.

　　“More children are going to bed with TVs on,and there are more opportunities(机会) to stay awake,with more homework,the Internet and the phone,” says Dr.Mary Carskadon,a sleep researcher at Brown University Medical School.She says these activities at bedtime can get kids all excited and make it hard for them to calm down and sleep.Other experts say part of the problem is chemical.Changing levels of body chemicals called hormones not only make teenagers’ bodies develop adult characteristics,but also make it hard for teenagers to fall asleep before 11 pm.

　　Because sleepiness is such a problem for teenagers,some school districts have decided to start high school classes later than they used to.Three years ago,schools in Edina,Minnesota,changed the start time from 7:25 am to 8:30 am.Students,parents and teachers are pleased with the results.

　　【语篇导读】研究表明,大部分美国孩子已经形成了不良的睡眠习惯。他们入睡晚,睡眠不足。其原因是电视、手机、网络、作业等一些令他们兴奋的事情影响了他们,导致身体内激素水平的变化,进而使得他们入睡晚。对此,学校也采取了改变上学时间等措施来解决此类问题。

　　1.What is the new National Sleep Foundation survey on?

　　A.American kids’ sleeping habits.

　　B.Teenagers’ sleep-related diseases.

　　C.Activities to prevent sleeplessness.

　　D.Learning problems and lack of sleep.

　　答案　A

　　解析　细节理解题。根据后文的介绍可知,美国“全国睡眠基金会”的调查针对的是美国10至18岁少年睡眠时间不足的情况及其影响,而不是疾病、失眠或学习问题。故选A项。

　　2.How many hours of sleep do 11-year-olds need every day?

　　A.7 hours. B.8 hours.

　　C.10 hours. D.18 hours.

　　答案　C

　　解析　细节理解题。根据第二段中的“For most school-age children,ten hours is ideal.”可知,对于11岁的孩子来说,每天10小时的睡眠时间是最理想的,故C项正确。

　　3.Why do teenagers go to sleep late according to Carskadon?

　　A.They are affected by certain body chemicals.

　　B.They tend to do things that excite them.

　　C.They follow their parents’ examples.

　　D.They don’t need to go to school early.

　　答案　B

　　解析　细节理解题。根据第三段中的“...these activities at bedtime can get kids all excited and make it hard for them to calm down and sleep.”可知,孩子们不睡觉的原因是他们在睡前倾向于做一些令他们兴奋的事情,故B项是根本原因。本题易误选A项,而根据“Other experts say...”可知A项所表述的并非是Carskadon的观点,故排除A项。

　　【长难句分析】Because sleepiness is such a problem for teenagers,some school districts have decided to start high school classes later than they used to.

　　因为嗜睡对青少年来说是个问题,一些学区决定中学上课的时间比以前晚一些。

　　本句是一个复合句。because引导的是原因状语从句,than引导的是比较状语从句。