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
The road in front of our school is _____ and is closed to all the cars
Kangkang won the first place in the _______ in the school sports meet last week.
y for the meeting________, they all left the conference room
What advice would you give to the young people who _________ you and who want to be like you