The dam will generate electricity _____ about 40 million tons of coal without causing so much air pollution.
| A．equal | B．be equal | C．equal to | D．be equal to |
This produced a chain reaction, _______ made _______ possible for life to develop.
| A．what; that | B．which; it |
| C．when; that | D．how; it |
The thought they couldthe whole continent was exciting.
| A．that; cross | B．what; cross |
| C．whether; across | D．when; across |
_________ life will continue on the earth for millions of years to come will depend on __________ this problem can be solved.
| A．If; that | B．Whether; if |
| C．If; whether | D．Whether; whether |
--May I open the window to let in some fresh air?
-- __________
| A．Come on. | B．Take care. |
| C．Go ahead! | D．Hold on! |
__________ is even more important is _________ the earth cooled down, water began to appear on its surface.
| A．What; that as | B．It; which |
| C．It; which as | D．What; which |