问题
选择题
Scientists are convinced the positive effect of laughter physical and mental health.
A．of; at
B．by; in
C．of; on
D．on; at
答案
C
be convinced of 确信。effect on……，有关于------方面的影响。
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Scientists are convinced the positive effect of laughter physical and mental health.
A．of; at
B．by; in
C．of; on
D．on; at
C
be convinced of 确信。effect on……，有关于------方面的影响。