Not until all the fish died in the river ____________ how serious the pollution was.
A. did the villagers realize
B. the villagers realize
C. the villagers did realize
D. didn’t the villagers realize
If he ___________ my advice then, he would not be in trouble now.
A. should take B. took
C. could take D. had taken
It doesn’t matter ___________ you turn right or left at the crossing — both roads lead to the park.
A. whether B. how
C. if D. when
It was in the school __________ he had studied ___________ he began the important experiment.
A. that; where B. in which; which
C. where; that D. where; in which
I felt somewhat sad and was about to leave _________ something happened which drew my attention.
A. unless B. until
C. when D. while
— May I stop here?
— No, you ___________.
A. mustn’t B. might not
C. needn’t D. won’t
