Scientists are convinced ______ the positive effect of laughter ______ physical and mental health.

A. of; at B. by; in

C. of; on D. on; at

We human beings should be very careful with what we do with nature, _____power is beyond our understanding.

A. that B. which C. whose D. where

—What’s all that noise about outside?

—Oh, I forgot to tell you. The road to the railway station ______.

A. will be widened B. is to be widened

C. has been widened D. is being widened

It was with the help of the local guide ______ the mountain climber was rescued.

A. who B. that C. when D. how

It doesn’t matter if they want to come to your party, ______?

A. doesn’t B. does it

C. don’t they D. do they

Only when he apologizes for his rudeness ______ to him again.

A. I will speak B. will I speak

C. do I speak D. I speak

One-third of the country ______ covered with trees and the majority of the citizens ______ black people.

A. is; are B. is; is

C. are; are D. are; is

The airport ______ next year will help promote tourism in this area.

A. being completed B. having been completed

C. completed D. to be completed

______ production up by 60%, the company has another excellent year.

A. As B. For C. With D. Through

Tim is in good shape physically ______ he doesn’t get much exercise.

A. if B. even though

C. unless D. as long as