He made another wonderful discovery, ____ of great importance to science.
| A．which I think is | B．which I think it is | C．which I think it | D．I think which is |
Please tell me the after service of the computer; I’m worried about a breakdown sometime．
| A．there being | B．it being | C．there is | D．it is |
—Jack can't concentrate on his lessons recently.
—Yes, that might ____ why he did so badly in the last test.
| A．answer for | B．apply for | C．call for | D．account for |
Theytwo free tickets to Australia, otherwise they’d never have been able to afford to go.
| A．had got | B．got | C．have got | D．get |
Not until they left school how much their teachers loved them and helped them.
| A．they realized | B．did they realize |
| C．had they realized | D．they would realize |
This new kind of chemicals will help keep the air, soil and water________ from pollution.
| A．free | B．empty | C．loose | D．short |