单项选择题

Scientists are convincedthe positive effect of laughterphysical and mental health.

A．of; at
B．by; in
C． of, on
D．on; at
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单项选择题
Now in China many young peopleimportant positions in the government.
A． seize
B．catch
C． grasp
D．hold
单项选择题
Information obtained from libraries is sooner forgotten than .
A．it from life
B．that from life
C．what from life
D．which from life
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