All of us found ( )difficult to work out the maths problem.

问题描述:

All of us found ( )difficult to work out the maths problem.
A.it B.that C.which D.what

A
如果用that
found 后面的从句就没有主语,这里需要你填写的就是主语
what则没有所指,which 也是一样,这句不是定语从句
find it **结构是常见的句市