A Brown 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 problems of adolescent  (青春期的) sleep at Brown’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.
  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 nigh 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 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, adolescent are up against difficulties when it comes to trying 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.”
28. Carskadon suggests that high schools should not start classes so early in the morning because________.
A. it is really tough for parents to enforce bedtime
B. it is biologically difficult for students to rise early
C. students work so late at night that they can’t get up early
D. students are so lazy that they don’t like to go to school early
29. The underlined phrase “nod off” most probably means “ _______”.
A. turn around      B. agree with others     C. full asleep    D. refuse to work
30. What might be a reason for the hard transfer middle school to high school?
A. Adolescents depend more on their parents.
B. Adolescents have to choose their sleep patterns.
C. Adolescents sleep better than they did at childhood.
D. Adolescents need more sleep than they used to.
31. What is the test mainly about?
A. Adolescent heath care.             
B. Problems in adolescent learning.
C. Adolescent sleep difficulties.     
D. Changes in adolescent sleep needs and patterns.
 28-31:BCDD  
28．答案:B 细节理解题。根据第一段最后一句话“Instead,it may be that biologically these sleepyhead students aren’t used to the early hour．”可知学生不应该起得太早来上课主要是因为他们身体里的生物钟不能适应这种程度的早起。
29．答案:C 词义猜测题。前后文主要说的是过于早起学习对孩子的影响问题，所以可推测出nod off应该意为“在课桌上打瞌睡”。这样的学生并不是懒惰而是有其身体方面的客观原因的。
30．答案:D 推理判断题。根据第四段、第五段全部内容和第六段第一句话可知青春期的孩子有很多方面的原因导致从初中到高中的转变及适应难度很大，其中之一就是到了高中睡眠时间要求比初中时多了，但这种睡眠方式的改变对学生来说想很快转变却很难。
31．答案:D 主旨大意题。由第一、二段引出话题到第三段点明主题，再到后面的展开论述，可总结归纳出本文的主要话题是关于“青少年睡眠需要和方式改变”，尤其是第三段的关键句“．．．she and her team are trying to learn more about how the biological changes of adolescence affect sleep needs and patterns”是明显的信息提示