It was nearly an hour the sleeping pill effect.
A. when; took
B. before; took
C. since; takes
D. before; would take
网友回答
A. when; took
(答案→)B. before; took
C. since; takes
D. before; would take
解析：考查固定句式和时态。本题中的固定句式：It be 一段时间 before…一段时间以后某事才发生；如果before后面使用一般现在时，前面的主语使用将来时；如果before后面使用一般过去时，前面也使用一般过去时；句意：一个小时以后安眠药片才开始生效。前后都使用过去时。故B正确。