题目内容：

    Take a look inside a high school classroom. You will most likely find a teacher at the front of the class and students sitting at their desks. Yet, look closer, and you might notice a familiar scene: many of these students are not paying attention. Instead, they are dozing off (打盹) or even completely asleep.

Today, the majority of high school students are not getting enough sleep. This lack (缺乏) of sleep is a serious problem, especially as students are doing more than ever with their time. They come to school early, spend hours listening to teachers and taking tests, and come home to be faced with even more work. And the homework load these days is not light; teachers give hours worth of homework each night.

Most kids need at least nine hours of sleep per night in order to function properly. Yet the period of this nine hours shifts as a child gets older. After puberty (青春期), the body’s internal clock changes so that it is difficult for teens to fall asleep before 11 p.m. So even if a student falls asleep at eleven, they would need to sleep until at least 8 a.m. to get a full night’s sleep. Considering the time at which most high schools in this country begin, those nine hours are clearly being shortened. Few high schools start after 8 a.m.

However，there are schools that have paid attention to this research and delayed the start of their school day. In schools where the start time is after 8:30 in the morning, the teachers believe that there has been a real change in their students. They note that the students miss class less, pay more attention in class, perform better in class, and report lower levels of depression (沮丧). The researchers of these studies say that the results are quite important and that more schools should consider delaying their start time of their school day.

1.The second paragraph mainly discusses _____ .

A.why high school students should get more sleep

B.The life of high school students at present

C.why high school students feel sleepy in the classroom

D.how to lighten high school students’ homework load

2.The underlined word “shifts” in Paragraph 3 probably means“______”.

A.arrives B.reduces

C.increases D.changes

3.How do the teachers feel about the results from delaying their school day?

A.Disappointed. B.Satisfied.

C.Puzzled. D.Surprised.