Scientists are convinced the positive effect of laughter physical and mental healthA. of

发布时间：2020-08-16 18:50:14

Scientists are convinced     the positive effect of laughter     physical and mental health．
A. of ;at
B. by; in
C. of ; on
D. on ;at

网友回答

A. of ;at
B. by; in
(答案→)C. of ; on
D. on ;at
解析：考查介词。be convinced of相信，名词effect后接on，故选C。
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