This new kind of chemicals will help keep the air, soil and water________ from pollution.
| A．free | B．empty | C．loose | D．short |
I won’t go and attend his wedding party ___, for his deeds have terribly hurt my feelings.
| A．if invited |
| B．even if invited |
| C．until invited |
| D．if not invited |
—Did the policeman let you in?
—No, ___ I told him who I was.
| A．if |
| B．once |
| C．as though |
| D．even if |
Young people today are living a much more comfortable life than their parents ___ several years ago.
| A．did |
| B．had |
| C．were |
| D．would |
He was about to leave ___ Tom arrived so he stayed a little longer.
| A．when |
| B．while |
| C．as |
| D．before |
Each statue is of a person who has made a ___ in American history.
| A．difference |
| B．improvement |
| C．significance |
| D．importance |