A、science fiction B、critical review C、science report D、textbook C

In the past twenty years, scientists have learnt a great deal about sleep and dreams. They have discovered, for example, that sleep and dreams affect the way people feel. A good night sleep, generally, makes a person happier in the morning.
   Dreams also have a strong effect on the moods of people. However, who appears in a dream is more important than what happens.
   Every person has a special dream character. If the special character appears in dreams, people are happier after sleeping. If there are many people in ones dreams, this has a good effect. A person will wake up happier.
   The moods of people affect their performance throughout the day. The level of ones moods rises and falls during the day. The less sleepy the people are, the better they perform, and usually they are more friendly, more aggressive, and more clear thinking.
   Some day scientists hope to manipulate sleep in order to control the way people feel and perform.