单项选择题

The best information in para. 5 is that______.

A．electricity from the energy of rivers can be produced
B．oil and coal are expensive to extract and transport
C．hydroelectric power has some advantages over coal and oil
D．waterfalls can be constructed by engineers

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单项选择题

In para. 6 the author______.

A．gives an example of ideal rivers for generating electricity
B．explains in detail what a suitable fiver for generating electricity should be
C．states that the amount of water in the fiver is very important
D．implies that the water plays an important role in industry

单项选择题

According to paragraphs 6 and 7,which is most fundamental in producing hydroelectric power ______.

A．Adequate flow of water
B．A steep fall
C．The location of the fiver
D．The amount of the water