B. when
(The children cheered wildly when the teacher let them play a game.)

D. rather than
(Nuclear science should be developed to benefit people rather than harm them.)

A. onlookers
(A crowd of onlookers had gathered around the old slum which was being demolished.)

C. Because of
(Because of the thunderstorm last night, our flight wouldn't have been delayed for hours.)

B. will he