单项选择题

The harm radiation has done to the Apollo crew members ______.

A．is insignificant
B．seems overestimated
C．is enormous
D．remains unknown
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单项选择题
According to the passage, a large population will produce a chance for developing ______.
A．agriculture
B．transport system
C．industry
D．national economy
单项选择题
The government of the developed countries may prefer to a ______ population.
A．stable
B．slowly-increasing
C．fast-increasing
D．declining
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