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Scientists are convinced ________ the positive effect of laughter ________ physical and mental health.
#25675
A
of; at
B
on; at
C
by; in
D
of; on
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______ all the texts that are written, stored and sent electronically, a lot of them are still ending up on paper.
#25729
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For
B
From
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Sorry. Madam. You’d better come tomorrow because it’s______the visiting hours.   
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during
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at
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He invited me to a dance after the show_______Christmas Eve.
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—I have booked a room ________two. —I’ll check, sir.
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____ the temperature falling so rapidly, we couldn't go on with the experience.
#29089
A
Since
B
With
C
As
D
For