He was afraid what he had done ______ a disastrous effect on his career.a. might have b. could be c. have been d. shall be
Experiments of this kind __________ in both the U. S. and Europe well before the Second World War.
It's no use __________ without taking action.
Even the best writers sometimes find themselves __________ for words.
I am afraid he's more of a talker than a doer, which is __________ he never finishes anything.
Claire had her luggage __________ an hour before her plane left.