Question

20. The agent was about to sign his name to the document    , to his surprise, a stranger broke in to prevent him.

A. while     B. when

C. as     D. until

Answer 1

20.   B考査状语从句的连接词。while虽然；when当……时候， 这时；as正如；until直到。句意：代理人刚要在文件上签字， 这时，让他惊讶的是，一个陌生人闯进来阻止了他。这里使用了固定结构be about to do when ...意为"刚要做……这时……"，所以选B。