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 (昼夜节奏的，生理节奏的) rhythm, helps control when you wake, when you eat and
when you sleep. Somewhere around puberty (青春期), something
happens in the timing of the biological clock. The clock pushes forward, so
adolescents (青少年的) 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 7.
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 ______.
A. it controls when we wake, when we eat and when we sleep
B. it has a cycle of 24 hours
C. it is a cycle also called circadian rhythm
D. it can alarm any time during 24 hours
【正确答案】
B
【答案解析】[解析] 细节题。用句中的your internal clock定位(即指a clock located inside our brains)，第一段第二句提供了答案。
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】[解析] 推理题。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。
单选题
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
单选题
According to the last two paragraphs, what did the previous researchers
think about the human eye's 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.
【正确答案】
B
【答案解析】[解析] 细节题。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 body's 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。