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
答案:C
convince 意为“使确信,说服”,与介词of连用,意为“使(人)承认或信服”。effect 意为“作用,功效,影响”,与介词on连用,表示“对……有影响”。