Last term our maths teacher set so difficult an examination problem none of us w

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

试题答案

B

解析:

as引导定语从句修饰"examination problem",在从句中作宾语,因其先行词前有限定词so。若看作"so…that…"结构,结果状语从句应加宾语,为"worked it out"。