Some people can stay up all night and still get work done the next day. I'm not one of them. After a night without enough sleep, I feel bad-tempered. I have trouble remembering things. And all I want to do is go to bed. How do you feel after you've stayed up late to finish schoolwork or the day after an overnight party? Scientists now say that your answers to these questions may depend on your genes.  New research suggests that a gene called "period 3" influences how well you function without sleep. The "period 3" gene comes in two forms: short and long. Everyone has two copies of the gene. So, you may have two longs, two shorts, or one of each. Your particular combination depends on what your parents passed on to you. Scientists from the University of Surrey in England studied 24 people who had either two short or two long copies of "period 3". Study participants   had to stay awake for 40 hours straight. Then, they took tests that measured how quickly they pushed a button when numbers flashed   on a screen and how well they could remember lists of numbers. Results showed that the people with the short form of "period 3" performed much better on these tests than the people with the long form did. In both groups, people performed worst in the early morning.  After the first round of experiments, participants were finally allowed to sleep. People in the group that performed well on the tests (those with the short form of "period 3") took about 18 minutes to nod off. While people with the long "period 3" gene fell asleep in just 8 minutes. They also spent more time on deep sleep. That suggests that people with the long form of the gene need more and deeper sleep to keep their brains working in top form. I think I must have the long form of "period 3". What about you? The purpose of this passage might be   _
to tell the result of a research on sleepy gene. to tell us the importance of plenty of sleep. to inform the harm of lacking sleep. to announce the sleeping rules of humans.
Question: Some people can stay up all night and still get work done the next day. I'm not one of them. After a night without enough sleep, I feel bad-tempered. I have trouble remembering things. And all I want to do is go to bed. How do you feel after you've stayed up late to finish schoolwork or the day after an overnight party? Scientists now say that your answers to these questions may depend on your genes.  New research suggests that a gene called "period 3" influences how well you function without sleep. The "period 3" gene comes in two forms: short and long. Everyone has two copies of the gene. So, you may have two longs, two shorts, or one of each. Your particular combination depends on what your parents passed on to you. Scientists from the University of Surrey in England studied 24 people who had either two short or two long copies of "period 3". Study participants   had to stay awake for 40 hours straight. Then, they took tests that measured how quickly they pushed a button when numbers flashed   on a screen and how well they could remember lists of numbers. Results showed that the people with the short form of "period 3" performed much better on these tests than the people with the long form did. In both groups, people performed worst in the early morning.  After the first round of experiments, participants were finally allowed to sleep. People in the group that performed well on the tests (those with the short form of "period 3") took about 18 minutes to nod off. While people with the long "period 3" gene fell asleep in just 8 minutes. They also spent more time on deep sleep. That suggests that people with the long form of the gene need more and deeper sleep to keep their brains working in top form. I think I must have the long form of "period 3". What about you? The purpose of this passage might be   _
A. to tell the result of a research on sleepy gene.
B. to tell us the importance of plenty of sleep.
C. to inform the harm of lacking sleep.
D. to announce the sleeping rules of humans.
Answer: