题目内容：

A Cornell University sleep researcher has some advice for people who run high schools: Don’t start classes so early in the morning. It may not be that the students who nod off at their desks are lazy. And it may not be that their parents have failed to enforce(确保) bedtime. Instead, it may be that biologically these sleepyhead students aren’t used to the early hour.

“Maybe these kids are being asked to rise at the wrong time for their bodies,” says Mary Carskadon, a professor looking at problem of adolescent (青春期的)sleep at Cornell’s School of Medicine.

Carskadon is trying to understand more about the effects of early school time in adolescents. And, at a more basic level, she and her team are trying to learn more about how the biological changes of adolescence affect sleep needs and patterns(方式).

Carskadon says her work suggests that adolescents may need more sleep than they did at childhood, no less, as commonly thought.

Sleep patterns change during adolescence, as any parent of an adolescent can prove. Most adolescents prefer to stay up later at night and sleep later in the morning. But it’s not just a matter of choice—their bodies are going through a change of sleep patterns.

All of this makes the transfer(迁移)from middle school to high school—which may start one hour earlier in the morning—all the more difficult, Carskadon says. With their increased need for sleep and their biological clocks set on the “sleep late, rise late” pattern, adolescents are up against difficulties when they try to be up by 5 or 6 a.m. for a 7:30 a.m. first bell. A short sleep on a desktop may be their body’s way of saying. “I need a timeout.”

1.Carskadon suggests that high schools should not start classes so early in the morning because

______.

A. students work so late at night that they can’t get up early

B. students are so lazy that they don’t like to go to school early

C. it is biologically difficult for students to rise early

D. it is really tough for parents to enforce bedtime

2.The underlined phrase “nod off” most probably means “_______”.

A. fall asleep    B. turn around

C. agree with others    D. refuse to work

3.Which of the following statements is NOT true according to Mary Carskadon?

A. Adolescents are going through a change of sleep patterns.

B. Adolescents need less sleep than they used to at childhood.

C. Adolescents prefer to stay up later at night and sleep later in the morning.

D. It is difficult for adolescents to get up early for a 7:30 a.m. first bell in high school.

4.What is the test mainly about?

A. Adolescent heath care.

B. Adolescent sleep difficulties.

C. Problems in adolescent learning.

D. Changes in adolescent sleep needs and patterns.