问题
Scientists are convinced ________ the positive effect of laughter _______ physical and mental health.
A:of at
B:by in
C:of on
D:on at
B:by in
C:of on
D:on at
正确答案是：
同类题型
Will you fix up the machine according to the , David—Yes, I will.
29 They made many records, _____ they will always be remembered
Wait till you are more ______.It’s better to be sure than sorry.[ ]
The reason Beethoven went away to the country is ______
“What are you busy for?”—This is a question we very often get _____ nowadays