I would appreciate __________ back this afternoon.
| A．you to call | B．your calling |
| C．you call | D．you are calling |
It was essential that the application forms ___________ back before the deadline .
| A．must be sent | B．would be sent |
| C．be sent | D．were sent |
_____________ cease（终止） advertising, prices would be significantly reduced.
| A．Were they to | B．Could they |
| C．If they | D．Would they |
Much labor would have been saved if the electronic computers_____________ before.
| A．had invented | B．were invented |
| C．should have been invented | D．had been invented |
There was a(n)________silence in the live interview，when no one knew what to say to the audience.
| A．ashamed | B．disappointed | C．desperate | D．awkward |
Doctors are doing research to find out what happens physically when people______ smoking.
| A．quit | B．decline | C．prevent | D．reserve |