Question

Our maths teacher set so difficult an examination problem ______ none of us worked out.

A．which

B．that

C．as

D．so that

Answer 1

C

解析试题分析：句意：我们的数学老师出了一个这么难的考试题，我们中没人能做出这个题来。这里是定语从句，so……as，as引导的是定语从句，as在从句中宾语，故选C。
考点：考查定语从句的用法。
点评：本题难度适中。定语从句是高中阶段必须掌握的语法项目，考生容易误选AB，这里是特殊的固定搭配，不能用that或which，在结果状语从句中that不作成分，故选C。
即学即练：I saw some trees，the leaves of  ______  were black with disease.
A. that        B. which        C. it         D. what
解析：B。考查非限制性定语从句的介词+which结构。the leaves of which 相当于 whose leaves。