Air pollution is getting more and more serious, so we must take action ________ it is too late.
#30412
A
before
B
after
C
until
D
when
推荐题目
You will have to stay at home all day ______ you finish all your homework.
#33127
A
if
B
unless
C
whether
D
because
—What's the party like?—Wonderful.It's years________I enjoyed myself so much.
#30060
A
after
B
when
C
before
D
since
Most birds find it safe to sleep in the trees, but ______ they have eggs or young chicks, they don’t use a nest.
#33314
A
why
B
how
C
where
D
unless
Even though they are not doubtful at all _______ John will pass the exam, I still wonder ______ he is fully prepared.
#34809
A
whether; that
B
that; whether
C
that; that
D
whether; whether