Question

Researches are convinced ______ the positive effect of laughter ______ physical and mental health.

A．of; at

B．by; in

C．of; on

D．at; on

Answer 1

C

试题分析：考查介词：be convinced of相信…，第二空填on，effect on…对…的影响，句意：研究者相信，笑声对身体精神健康的积极影响。选C。
点评：本题考查了介词短语，在平时要加强识记和记忆。做题时要结合上下文判断。