Scientists are convinced ___ the positive effect of laughter ___ physical and mental health.
| A．of; at | B．by; in | C．of; on | D．on; at |
Dad ______ a lot of alcohol, but now he has given that up and ______ soft drinks.
| A．used to drink; is used to drinking | B．was used to drinking; used to drink |
| C．used to drink; used to drinking | D．was used to drink; is used to drink |
The guards caught the spy and _____ him very carefully.
| A．searched for | B．searched | C．look for | D．asked for |
I have no doubt _____ he will get the first place in the competition.
| A．whether | B．if | C．that | D．About |
He’s given me so much help that I really want to do something for him _____.
| A．in turn | B．by turns | C．in return | D．in answer |
The heavy rain has lasted for several days and the river has______ by 30 centimeters.
| A．risen | B．raised | C．arisen | D．lifted |