单项选择题

Clouds are formed from ______.

A．water vapor
B．evaporation
C．the hydrologic cycle
D．groundwater
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单项选择题
The supply of groundwater is getting low because of ______.
A．conservation
B．toxic waste
C．pollution
D．population increase
单项选择题
According to the author, greenspace facilities should be designed in such a way that ______.
A．more obligatory activities might take on a recreative aspect
B．more and more people might have access to them
C．an increasing number of recreative activities might be developed
D．recreative activities might be brought into our homes
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