【题目】—What happened in the hall?
—I don’t know. People began to rush out ________ I realized what was happening.

A. while

B. when

C. after

D. before

【答案】D

【解析】考查时间状语连词。A. while当……时；B. when当……时；C. after在……之后；D. before在……之前。句意：——大厅里出什么事了？——我不知道。在我意识到发生什么之前人们就开始往外冲了。故选D。