This was such a ___ test ____ few of the students could work out.

题目

This was such a ___ test ____ few of the students could work out.
A.difficult,that B.challenging,as 为什么选B,不选A?

答案

B as 引导定语从句,并且替代先行词 a challenging test 在从句中做的是 work out的宾语.
如果是A 的话,such ……that 引导一个完整的结果状语从句.应该是：
This was such a difficult test that few of the students could work it out.