单项选择题

The amount of sleep required may ______ .

A．vary greatly from one individual to another
B．depend on an individual's age
C．be related to an individual's occupation
D．all of the above
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单项选择题
If a person is not allowed to follow his sleep routine, he will probably ______ .
A．not sleep well
B．never fall asleep
C．lose his memory
D．begin to daydream
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