He was famous as a doctor before_____(join) the film industry.

题目

He was famous as a doctor before_____(join) the film industry.
joined
为什么?

答案

答案应该是joining
如果用joined,应为before he joined the ...
before后接动词ing形式,表示主动.相当于before he joined teh film industry.
译文：
加入电影业前,他是个著名的医生.