单项选择题

According to the passage, sea-water can be turned into fresh water by

A．heating it up.
B．treating it with chemicals.
C．taking salt out of it.
D．drying it up.

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单项选择题

According to the passage, we can avoid a worldwide water shortage in the future by

A．increasing rainfall.
B．reusing water and utilizing sea-water.
C．cutting down our consumption of water.
D．reducing the number of factories producing steel.

单项选择题

What percentage of the earth's water can man actually use at present

A．Nearly 75 per cent.
B．About 97 per cent.
C．Exactly 3 per cent.
D．Less than 3 per cent.

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