. As a teacher, he has never given his students so difficult a problem they can’t work ou

发布时间：2020-08-16 07:19:18


. As a teacher, he has never given his students so difficult a problem      they can’t work out.
A. if
B. that
C. when
D. As

网友回答

A. if
B. that
C. when
(答案→)D. As
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