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 Scientists say it will be five or six years __________ it is possible to test this medicine on humans.
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after
B
before
C
since
D
when
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The day breaks，______ the birds are singing.
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A new shopping centre will be built        the old fish market used to be.
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—May I go outside and play for a while, Dad?—No, you can’t ____ your homework is being done.
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 Don’t speak in such a manner, _____ you’ll get into trouble.
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That’s all for the introduction to your arrangements these days. So now ______ there are any questions, I’d like to go ahead and start the first video.
#31607
A
if
B
unless
C
until
D
though