Scientists are convinced_____the positive effect of laughter_____physical and mental health.     
#28733
A
of; at
B
by; in
C
of; on
D
on;at
推荐题目
When we ran to the top of the hill, we were _____ .
#26962
A
out of fashion
B
out of work
C
out of the question
D
out of breath
 It is illegal for a public official to ask people for gifts or money          favors to them.
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A
in preference to
B
in place of
C
in agreement with
D
in exchange for