Hard as a teacher may try he can’t to make all his students make a difference in study l

问题补充：

Hard as a teacher may try, he can’t to make all his students make a difference in study, letting alone in life.

A. make sure

B. be sure

C. guarantee

D. insure

答案：

A. make sure

B. be sure

(答案→)C. guarantee

D. insure

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