Every possible means ______ to prevent the air pollution, but the sky is still not clear.
A. has been used B. have been usedC. is used D. are used
My father and my mother have been married for 30 years, and never once ______ with each other.
A. they have quarrelledB. did they quarrel
C. had they quarrelledD. have they quarrelled
Although the old man was ______ death, he still fought with the disease bravely.
A. at the end of B. on the top of
C. at the edge of D. on condition that
Many countries are increasing their use of natural gas, wind and other forms of ______.
A. energy B. power C. force D. strength
It may not be a great suggestion. But before ______ is put forward, we will make do with it..
A. a best one B. the best one C. a better one D. a good one
Try not to cough more than you can ______ since it may cause problems to your lungs.
A. help B. stop C. allow D. check
