A、 There are many controversial issues like the right amount of sleep.
B、 Among many issues the right amount of sleep is the least controversial.
C、 People are now moving towards solving many controversial issues.
D、 The right amount of sleep is a topic of much controversy among doctors.

【正确答案】 D

【答案解析】解析：睡眠时间多少合适是医生们争议的话题。

A、 Because few people can wake up feeling fresh and alert.
B、 Because some people still feel tired with enough sleep.
C、 Because some people still feel sleepy with enough sleep.
D、 Because some people go to bed very late at night.

【正确答案】 C

【答案解析】解析：从“If he is right many people must be undersleeping，including myself．”可推知。

A、 Sleeping less is good for human development.
B、 People ought to be persuaded to sleep less than before.
C、 It is incorrect to say that people sleep too little.
D、 Those who can sleep less should be encouraged.

【正确答案】 D

【答案解析】解析：作者指出，有些人天生可以睡眠少于平均水平而保持良好的状态。

A、 The author comments on three different opinions.
B、 The author favors one of the three opinions.
C、 The author explains an opinion of his won.
D、 The author revises someone else's opinions.

【正确答案】 A

【答案解析】解析：文章分别叙述了三种观念，作者反驳了第一种观念，对后两种持肯定态度。

A、 Because their bodies are fatigued
B、 Because some people have a greater inertia than others.
C、 Because they fall asleep quickly and they are reluctant to get up.
D、 Because must make up for the lost sleep.

【正确答案】 B

【答案解析】解析：因为有些人的惰性较强，转换状态较慢。