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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
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He was a good student and scored _________ average in most subjects.
#26857
A
below
B
of
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on
D
above
She said she would spend her holiday ___ Beijing.
#28169
A
on
B
at
C
in
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For
 He is always helping people without expecting anything _____.
#26277
A
in common
B
in turn
C
in danger
D
in return
The railway will be opened______traffic＿＿＿ May 1, 2009.
#28351
A
to； on
B
to； in
C
by； on
D
for； on
Thank you for your help and I hope I can do something for you_____.
#27264
A
in return
B
in turn
C
in reply
D
by turns