I the office yesterday afternoon when a stranger came in with a boy．
A. left
B. was about to leave
C. was to have left
D. will leave
网友回答
A. left
(答案→)B. was about to leave
C. was to have left
D. will leave
解析：
这题考查词组：be about to do …when…“刚要做…这时”，句意是：昨天下午我刚要离开办公室这时一个陌生人带着个孩子进来了。选B。