Question

【题目】Scientists are convinced _______ the positive effect of laughter _______ physical and mental health.

A.in; onB.of; onC.on; atD.in; at

Answer 1

【答案】B

【解析】

考查介词。句意：科学家们确信笑对身心健康有积极的影响。be convinced of是固定句式，意为“相信……”；effect经常和on搭配，表示“对……的影响”。故选B。