单选题

Making Light of Sleep

All we have a clock located inside our brains. Similar to your bedside alarm clock, your internal clock runs on a 24-hour cycle. This cycle, called a circadian rhythm, helps control when you wake, when you eat and when you steep.
Somewhere around puberty, something happens in the timing of the biological clock. The clock pushes forward, so adolescents and teenagers are unable to fall asleep as early as they used to. When your mother tells you it"s time for bed, your body may be pushing you to stay up for several hours more. And the light coming from your computer screen or TV could be pushing you to stay up even later.
This shift is natural for teenagers. But staying up very late and sleeping late can get your body"s clock out of sync with the cycle of light and dark. It can also make it hard to get out of bed in the morning and may bring other problems, too. Teenagers are put in a kind of a gray cloud when they don"t get enough sleep, says Mary Carskadon, a sleep researcher at Brown University in Providence, RI. It affects their mood and their ability to think and learn.
But just like your alarm clock, your internal clock can be reset. In fact, it automatically resets itself every day. How? By using the light it gets through your eyes.
Scientists have known for a long time that the light of day and the dark of night play important roles in setting our internal clocks. For years, researchers thought that the signals that synchronize the body"s clock were handled through the same pathways that we use to see.
But recent discoveries show that the human eye has two separate light-sensing systems. One system allows us to see. The second system tells our body whether it"s day or night.

单选题 The clock located inside our brains is similar to our bedside alarm clock because ______.

【正确答案】 B

【答案解析】本题问的是人脑内的生物钟与床头的生物钟相似的原因。原文第一段的第二句话明确说到，“Similar to your bedside alarm clock, your internal clock runs on a 24-hour cycle.”该句话中的your internal clock指的就是a clock located inside our brains。可见，它们的相似之处就在于都以24小时为一个周期。因此，本题的正确答案为B。

单选题 What is implied in the second paragraph?

A、 Young children"s biological clock has the same rhythm with that of the teenagers.
B、 People after puberty begin to go to bed earlier due to the change of the biological clock.
C、 Children before puberty tend to fall asleep earlier at night than adolescents.
D、 Teenagers go to bed later than they used to due to the light from the computer screen.

【正确答案】 C

【答案解析】本题问的是第二段中暗示了什么信息。根据题干定位至原文的第二段。该段主要讲的是，过了青春期(puberty)，由于生物钟节奏的变化，青少年比以前要晚睡几个小时。也就是说，青春期以前的孩子比处于青春期的青少年睡得更早。只有C选项符合题意，而其它三个选项的内容均与原文内容相反。因此，本题的正确答案为C。

单选题 In the third paragraph the author wants to tell the reader that ______.

【正确答案】 B

【答案解析】本题问的是第三段想要告诉读者什么信息。根据题干定位至原文的第三段。该段的最后一句话明确说到，“It affects their mood and their ability to think and learn.”晚睡会影响青少年的心情以及思考和学习能力。因此，本题的正确答案为B。

单选题 Which of the following statements is NOT true according to the fourth and fifth paragraphs?

【正确答案】 C

【答案解析】本题问的是根据第四、五段内容，哪一项是错误的。根据题干定位至原文的第四、五两段。根据这两段的内容可知，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光线来自动调节生理节奏。可见，A、B和D三个选项均与原文内容相符。但是根据常识也可判断，闹钟不能自动重新设定时间，故C选项的说法错误。因此，本题的正确答案为C。

单选题 According to the last two paragraphs, what did the previous researchers think about the human eye"s light-sensing system?

【正确答案】 B

【答案解析】本题问的是根据最后两段，之前的研究者对眼睛感光系统的认识。根据题干定位至原文的最后两段。最后一段的第二句话明确说到，“For years, researchers thought that the signals that synchronize the body"s clock were handled through the same pathways that we use to see.”多年来，研究者一直认为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。而第三句话接着说到，“But recent discoveries show that the human eye has two separate light-sensing systems.”但最新发现，人的眼睛有两个感光系统。由此可推知，研究者之前认为人类的眼睛只有一个感光系统。因此，本题的正确答案为B。