Last term our maths teacher set so difficult an examination problem _____ none of us worked out.
A. that
B. as
C. so that
D. which
出自:国家开放大学英语语法

完成拼图验证

按住下方滑块,将拼图拖到缺口处后松开。

拼图背景,将小拼图拖到缺口处
向右拖动滑块