阅读理解 If someone is sleepwalking, they are walking around while they are asleep. Sleepwalking happens when a person is not fully asleep but not quite awake. Usually we move from our deepest level of sleep to a lighter level and stay there. Sleepwalkers come right up to wake levels but do not fully awaken. It is at this time that they get up and walk.
The longer a person stays in deep sleep, the more time it takes for the sleep to be broken. That opens up the possibility of being awakened (but not fully) and of sleepwalking.
Sleepwalking happens more often among young people than grown-ups because young people usually have more deep sleep. Up to 7% of 5 to 12-year-olds sleepwalk, while only about 2% of grown-ups sleepwalk. We get less deep sleep as we are getting older and the possibility of sleepwalking is also reduced.
Sleepwalking may run in families, too. If one of your parents was a sleepwalker, you have about a 50% possibility of also being a sleepwalker.
单选题 This passage is about______.
【正确答案】 A
【答案解析】通读全文可知，文章主要介绍了梦游症产生的原因、年龄和概率等，所以A项最符合题意。
单选题 Who has more possibility of sleepwalking?
【正确答案】 B
【答案解析】根据第三段第一句“Sleepwalking happens more often among young people than grow-ups…”可知，梦游症发生在年轻人身上的概率更高。故选B。
单选题 What does " reduced" mean in "... the possibility of sleepwalking is also reduced" in Paragraph Three?
【正确答案】 B
【答案解析】open up：开始；cut down：减少；keep on：继续；speed up：加速。由句中的also一词可知，reduce应与前面的get less(变少)意思相近。故选B。
单选题 People have more possibility of developing sleepwalk______.
【正确答案】 C
【答案解析】根据文章最后一句可知，如果你的父母有一方是梦游症患者，那么你患梦游症的概率为50％，这比正常人要高很多，所以选项C正确。根据第三段最后一句“…we are getting older and the possibility of sleepwalking is also reduced．”可知，选项A错误；B、D两项并未在文中提及。故选C。
单选题 This passage may be from______.
【正确答案】 C
【答案解析】本文主要介绍了“梦游症”这一生理现象，属于科学范畴。故选C。