Estuaries provide both recreation and education for human beings. They also _____ the economy through tourism and fishing.
| A．contribute to | B．adapt to | C．respond to | D．apply to |
We used to work in the same office and we _________ have coffee together.
| A．would | B．should | C．could | D．might |
_____ all the inventions have in common is ______ they have succeeded.
| A．What; what | B．That; what | C．What; that | D．That; that |
The new machine，if _________ properly，will work at least ten years.
| A．use | B．using | C．being used | D．used |
—What were you doing when the telephone rang?
—I ______ away my books and ______ to bed.
| A．had just put;was going | B．was just putting;went |
| C．just put;had gone | D．have just put;gone |
I thought Jim would say something about his school report,but he ______ it.
| A．doesn’t mention | B．hadn’t mentioned | C．didn’t mention | D．hasn’t mentioned |