Question

【题目】Peter had been puzzled over the problem for over an hour___________ all at once the solution flashed across his mind.

A.whenB.whileC.thenD.as

Answer 1

【答案】A

【解析】

考查状语从句连词。句意：Peter已经被这个问题困扰一个多小时了，突然解决方法从他脑海里闪过。A. when当……时候；B. while当……时候，尽管，然而；C. then然后；D. as当，因为，尽管。分析句子可知，此处考查固定句型had done…when…“已经/刚做完某事……（突然）就……”，故选A项。