We see the lightning _____ it appears, but we hear the thunder a moment later.
A. the instant
B. for an instant
C. on the instant
D. in an instant
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_____ the world began,it has been difficult for nations to keep peace with their neighbors.
Although
B. When
C. Until
D. Ever since
Yesterday morning a prisoner escaped from the prison. It was a long time _____ the guards find out what had happened.
A. before
B. until
C. since
D. when
The sound of the piano became fainter and fainter _____ it was not heard any longer.
A. since
B. after
C. until
D. as soon as
Not until the mother shouted at the top of her voice _____ his head.
A. that the boy turned
B. did the boy turn
C. the boy didn't turn
D. the boy had turned