问题补充:
The famous scientist was going out he found himself surrounded by lots of young people.
A. when
B. before
C. while
D. after
答案:
(答案→)A. when
B. before
C. while
D. after
解析:考查固定搭配,was/were doing….when….,刚要做什么,这时,句意:著名的科学家刚要出去,这时他发现自己被一群年轻人围住了,选A。