问题
选择题
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
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。