I know Mr Brown；we _____ to each other at an international conference.
| A．are introduced | B．have been introduced |
| C．were introduced | D．had been introduced |
I have no idea ____________ measures the government will take to stop the river from being further polluted.
| A．which | B．what | C．that | D．whose |
Scientists are convinced __________ the positive effect of laughter _________ physical and mental health.
| A．of; at | B．by; in |
| C．of; on | D．on; at |
The little girl __________ the money for herself, but she __________ it away.
| A．could have used; gave | B．would use; gave |
| C．could have used; had given | D．would use; had given |
He was caught in the rain, __________ himself catch a cold.
| A．having made | B．making |
| C．to make | D．made |
It _______ we had stayed together for a couple of weeks _______ I found we had a lot in common.
| A．was until; when | B．was until; that |
| C．wasn’t until; when | D．wasn’t until; that |