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You should inspect the wheels regularly, and replace them ______ they cause you trouble.
#31371
A
while
B
as
C
before
D
until
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 —How was that? —I was chatting on line ______ the power went out.
#30936
A
because
B
while
C
as
D
when
________scores of times, but Derek still couldn’t understand how to use past participle in a concrete situation.
#32441
A
Having explained
B
Having been explained
C
Though it was explained
D
It was explained
— What is that building?— _____ the garden equipment is stored.
#80640
A
There is in which
B
That is where
C
The building that
D
That I got
_________ caused the accident is still a mystery.
#30978
A
How
B
What
C
That
D
Where
Mother told her son that it would be half a year ______ she could come back from American.
#32344
A
since
B
before
C
that
D
when