3. In the third paragraph the author wants to tell the reader that
A it is natural for teenagers to stay up late and get up late.
B staying up late has a bad effect on teenagers ability to think and learn.
C during puberty most teenagers experience a kind of gray cloud.
D it is hard for teenagers to get out of bed in the morning.
4. Which of the following statements is NOT true according to the fourth and fifth paragraphs?
A Our biological clock resets itself automatically.
B light gets through our eyes and resets our biological clock.
C Our internal clock as well as the alarm clock can be reset automatically.
D Our internal clock，like the alarm clock，can be reset.
5. According to the last two paragraphs， what did the previous researchers think about the human eyes light-sensing system?
A The human eye had two light-sensing systems.
B The human eye had one light-sensing system.
C The human eye could sense the light of day more quickly than the dark of night.
D The human eye could reset our internal clocks in accordance with the alarm clocks.
答案与题解：
1.B 第一段第二句提供了答案。句中的your internal clock 即指a clock located inside our
Brains.
2. C 第二段主要内容是告诉读者，过了青春期（puberty），由于生物钟节奏的变化，青少年（adolescents and teenagers）比以前要晚睡几小时。所以C是该段所隐含的内容。
3. B 第三段的最后一句直接给出了答案。
4. C 根据第四和第五段的内容，闹钟和生物钟都可以重新设定时间，但生物钟能通过眼睛接
受的日光来自动调节生理节奏。所以A、B和D都是这两段中所述内容，C是正确选择，因为闹钟不能自动重新设定时间。
5.B 问题使用的是过去时，问的是研究者在最新发现（recent discoveries）之前对眼睛感光系统的认识，即，the signals that synchronize the bodys clock were handled through the same
pathways that we use to see （眼睛所接受到的平衡生物钟的光信号同样作用于人类的视觉系
统），也就是说，研究者之前认为人类的眼睛只有一个感光系统。但最新发现却是，人的眼睛有两个感光系统。