The agent was about to sign his name to the document ，to our surprise，a stranger broke in

发布时间：2020-08-17 10:13:42

The agent was about to sign his name to the document     ，to our surprise，a stranger broke in to prevent him.
A. while
B. when
C. as
D. until

网友回答

A. while
B. when
C. as
D. until
解析：B
解析　when此处为并列连词，相当于at that time，可译为“这时(突然)……”。
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