题目内容：

A special laboratory at the University of Chicago is busy only at night. It is a dream laboratory where researchers are at work studying dreamers. Their findings have discovered that everyone dreams from three to seven times a night, although in ordinary life a person may remember none or only one of his dreams.

　　While the subjects—usually students—sleep, special machines record their brain waves and eye movements as well as the body movements that signal the end of a dream. Surprisingly, all subjects sleep soundly.

Observers report that a person usually fidgets(烦躁不安) before a dream. Once the dream has started, his body relaxes and his eyes become more active, as if the curtain had gone up on a show. As soon as the machine shows that the dream is over, a buzzer wakens the sleeper. He sits up, records his dream, and goes back to sleep—perhaps to dream some more.

Researchers have found that if the dreamer is wakened immediately after his dream, he can usually recall the entire dream. If he is allowed to sleep even five more minutes, his memory of the dream will have disappeared.

1.According to the passage, researchers at the University of Chicago are studying ____.

A．contents of dreams　                    B．dreamers while they dream

C．the meaning of dreams                   D．the progress of sleeping

2.Their finding has discovered that _____.

A．everyone dreams every night

B．dreams are easily remembered

C．dreams are likely to be frightening

D．One person dreams only one dream a night

3.The machines being used in the experiment record _____.

A．the depth of sleep

B．the subjects’ brain waves and eye movements

C．how many dreams a person has

D．what a sleeper dreams during his sleep

4.A person would be most likely to remember the dream that _____.

A．was of most interest to him

B．occurred immediately after he went to sleep

C．occurred just before he woke up

D．was the longest one to him