Scientistsareconvinced.

問題詳情：

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

A. of; at                       B. by; in                C. of; on               D. on; at

【回答】

解析：選C。句意：科學家們堅信笑對身心健康有積極影響。be convinced of=be completely sure about sth. 堅信，深信，確信；effect常與on連用，表示“對……的影響”。以上兩個均屬於固定搭配。

知識點：介詞

題型：選擇題