Scientists are convinced _____ the positive effect of laughter _____ physical and mental health.
| A．of; at | B．by; in | C．of; on | D．on; at |
It was about 600 years ago __________ the first clock was made.
| A．that | B．until | C．before | D．when |
He is wearing sunglasses to __________ his eyes from the strong sunlight.
| A．protect | B．prevent | C．save | D．help |
The policemen are searching _____ every house _____ the thief.
| A．for; for | B．of; of | C．不填; for | D．of; for |
. The book, _______ is blue, is mine.
| A．the cover of which | B．whose cover |
| C．of which the cover | D．all the above |
Paul didn’t want to put on the coat. He said that he _________ by his friends.
| A．will be laughed at | B．will be laughed |
| C．would be laughed at | D．would be laughed |