题目内容：

Last term our maths teacher set so difficult an examination problem ( )none of us work out.A that B
Last term our maths teacher set so difficult an examination problem ( )none of us work out.
A that B as C so that D which
答案为什么是AS呢,怎么也不理解

优质解答

你想选that吧?
选that的话,work out的后面要加一个it的
这里选as是引导定语从句的