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Last term our maths teacher set so difficult an examination problem _____ none of us worked it out. 

A. that    B. as    C. so that    D. which

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

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

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

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