_______, there would be no air around the earth.
| A．There were no gravity | B．There was not any gravity |
| C．Were there no gravity | D．was there no gravity |
Some students often listen to music _____ classes to refresh themselves.
| A．between | B．among | C．over | D．during |
.—____ when has the country been open to international trade?
—1978, I suppose.
| A．Since | B．In | C．From | D．After |
I think he is taking an active part in social work. I agree with you ______ .
| A．in a way | B．on the way | C．by the way | D．in the way |
Experts have been warning _____ of the health risks caused by passive smoking.
| A．at a time | B．at one time | C．for some time | D．for the time |
He was told that it would be at least three months ___ he could recover and return to work.
| A．when | B．before | C．since | D．that |