Lawrence Craven, a doctor from the USA, is the author of several published reports, one of ________ introduced the idea in 1953 ________ aspirin could reduce the risk of heart attacks.
| A．them; when | B．which; that |
| C．what; that | D．which; when |
— Has Sam finished his homework today?
— I have no idea. He ________ it this morning.
| A．did | B．was doing | C．has done | D．had done |
— I heard they went skiing in the mountains last winter.
— It ________ true because there was little snow there.
| A．may not be | B．won’t be | C．couldn’t be | D．will be |
The position, however, ________ you are applying, is not quite a wellpaid one.
| A．that | B．for which | C．which | D．to which |
Cultural exchange ________ better understanding.
| A．makes for | B．looks for | C．takes for | D．sends for |
You can come here to ask me ________ if you have any questions.
| A．at one time | B．at a time | C．at any time | D．all the time |