单项选择题

Experiments show that ______.

A．caffeine users can sleep longer than non-users
B．non-users usually fall asleep more easily than caffeine users
C．caffeine can help people to fall asleep
D．caffeine users wake up more early than non-users

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单项选择题

Which of the following does not contain caffeine, according to the passage

A．cola drinks
B．tea
C．chocolate and cocoa
D．water

单项选择题

The main point discussed in this passage is ______.

A．the harmful effects of coffee on people
B．the harmful effects of caffeine on people
C．caffeine used as a viable cure for momentary fatigue
D．excessive ingestion of caffeine by people