The number of foreign students attending Chinese universities ________ rising steadily since1990. 
| A．is | B．are | C．has been | D．have been |
John shut everybody out of the kitchen ________ he could prepare his grand surprise for the party.
| A．which | B．when | C．so that | D．as if |
________ the police thought he was the most likely one，since they had no exact proof about it，they could not arrest him.
| A．Although | B．As long as |
| C．If only | D．As soon as |
The medicine works more effectively ________ you drink some hot water after taking it.
| A．as | B．until | C．although | D．if |
Owen wouldn't eat anything ________ he cooked it himself.
| A．until | B．since | C．unless | D．while |
You will be successful in the interview ________ you have confidence.
| A．before | B．once | C．until | D．though |