Scientists say it may be five or ten years___________ it is possible to test this medicine on human patients.
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A
since
B
before
C
after
D
when
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_____there are many different types of food, some animals spend their lives eating only one type.
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A
Since
B
As
C
Despite
D
While
I think you should complain ---________ of course, you are happy with the way things are.
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A
if
B
unless
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as
D
because
He was allowed to go swimming _______ he kept near the other boys.
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on condition that
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as far as
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even if
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as though
Why did they keep trying _________ they must have known it was hopeless?
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A
if
B
because
C
when
D
whether