There is an endless supply of stories about sleepwalkers（梦游者）. Persons have been said to climb on roofs, solve mathematical problems, write music, walk through windows, and do murder in their sleep.
In Revere, Massachusetts, a hundred policemen searched for a lost boy who left his home in his sleep and woke up five hours later on a strange sofa in a strange living room, with no idea how he had got there.
At the University of Iowa, a student was reported to have the habit of getting up in the middle of the night and walking three quarters of a mile to the Iowa River. He would take a swim and then go back to his room to bed.
An expert on sleep in America claims（声称）that he has never seen a sleepwalker. He is said to know more about sleep than any other man alive, and during the last thirty-five years he has lost a lot of sleep watching people sleep. He says, Of course, I know that there are sleepwalkers because I have read about them in the newspapers. But none of my sleepers ever walked, and if I were to advertise for sleepwalkers for an experiment, I doubt whether I could get many takers.
Sleepwalking, however, is a scientific reality. It is one of those strange things that sometimes look quite like the fantastic（怪诞的）. Doctors say that sleepwalking is much more common than is generally supposed. Many sleepwalkers do not try to find help and are never recorded.
21．Generally speaking, sleepwalkers are the ones that ________.
A. can climb on roofs
B. can walk through windows
C. can do fantastic things during their sleep
D. can walk in a half-awake state
22．It was reported that a boy ________.
A. was found on a strange sofa, telling how he had got there
B. slept in his own room but woke up in a strange room
C. lost his way five hours after he left home
D. was searched for by policemen for he lost his way
23．The passage mentions a college student who got into the habit of ________.
A. getting up in the middle of the night and walking out
B. walking three quarters of a mile every day
C. swimming in the Iowa River before going to bed
D. walking about before he went to bed
24．An American expert knows more about sleep than any other man alive, ________.
A. because he can get many takers for his experiment
B. because he has had trouble with sleep for 30 years
C. but he says he has never seen sleepers walk
D. but he has nobody to sleep together with him
25．People think sleepwalking is nothing but one of the fantastic things without any explanation. Why
A. It is so common that it neednt be recorded.
B. Scientists take no interest in it.
C. Doctors dont want to care about it.
D. No records about it have been made.
Key:
21-25 CBACD