(2013·潍坊高考模拟)Air pollution is getting more and more serious，so we must take action________it is too late.
#30055
A
before
B
after
C
until
D
when
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All the photographs in this book，________ stated otherwise，date from the 1950s.(2012·陕西，25)
#30219
A
unless
B
until
C
once
D
if
Being a doctor is one of the few professions＿＿＿＿if you make a mistake，it can mean somebody's life．
#31095
A
that
B
which
C
when
D
where
—Do you think the weather will be all right this summer? —No, ____ we are lucky. The newspaper says it’ll be very hot anyway.
#31353
A
if
B
though
C
unless
D
as
I coutdn't have got to the meeting on time____________ an earlier train.
#80331
A
if I had not caught
B
unless I had caugh
C
if ! did not catch
D
unless I caugh