Under the environment of fierce competition, the only way John could imagine _______ stress was to get tougher by making greater efforts.
Not until all the fish died in the river ____________ how serious the pollution was.
If he ___________ my advice then, he would not be in trouble now.
It doesn’t matter ___________ you turn right or left at the crossing — both roads lead to the park.
It was in the school __________ he had studied ___________ he began the important experiment.
I felt somewhat sad and was about to leave _________ something happened which drew my attention.