单项选择题

From the passage we can draw the conclusion that long periods of sleeplessness may produce ______.

A．lasting harm to the brain
B．a loss of cheerfulness forever
C．no permanent damage
D．some serious after-effects
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单项选择题
After 72 hours without sleep, Tripp ______.
A．showed mental disorder
B．saw imaginary worms
C．was unable to stand
D．tried to run away from the building
单项选择题
What is the author's attitude toward the claims made by advocates of health foods
A．very enthusiastic.
B．somewhat favorable.
C．neutral.
D．skeptical.
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