Scientists are convinced _____ the posit
题型:选择题
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
Scientists are convinced _____ the positive effect of laughter _____ physical and mental health.[ ]
A. of; at
B. by; in
C. of; on
D. on; at