题目内容：

It is a common sense that new ideas have to be tested many times before ___
A being fully accepted
B fully accepted
before 后不能省略吗？

优质解答

A. 新想法在被接受之前要经过多次检验,这是常识.
before是介词,后面要用动名词结构的.这里还有个被动的关系在里面.因此不用A而选择B.
作连词的话B选项应该是they're fully accepted (by people)
语法上可以把before以及before后面的全部去掉,但是句意有点不完整了.

追问：

我的意思是，before 后面 It is a common sense that new ideas have to be tested many times before (they were) fully accepted 的they were 能不能直接省略，不是加being ？

追答：

我感觉口语上应该可以，其实回答之前我也纠结了一会儿。不过既然这里出了这一道题，而又有A选项在这里，从做题的角度看，选A好一点。