16. How long do teenagers need to sleep at least every day?
A. Seven hours. B. Eight hours. C. Nine hours.
17. What time do people feel the sleepiest during a day?
18. The writer proves a lack of sleep plays a role in accidents by ________.
A. asking questions B. listing numbers C. giving examples
19. Which of the following can be put in ▲ ?
A. SUGGESTIONS B. FACTS C. PROBLEMS
【答案】16. B 17. A 18. C 19. B
【导语】本文主要介绍关于睡眠的相关事实。
【16题详解】细节理解题。根据“Teenagers 8-10”可知，青少年需要8-10小时的睡眠，所以是至少8小时。故选B。
【17题详解】细节理解题。根据“Tiredness usually peaks twice a day, at 2 a.m. and 2 p.m.”可知，疲劳通常在一天中达到高峰两次，即凌晨两点和下午2点。故选A。
【18题详解】细节理解题。根据④部分的介绍可知，作者通过举例证明睡眠不足是造成事故的原因之一。故选C。
【19题详解】推理判断题。本文主要介绍关于睡眠的相关事实，故选B。
