—How should we deal with air pollution?
题型:选择题
问题:
—How should we deal with air pollution?
—It will be very difficult _____ there are fewer factories and cars.[ ]
A. until
B. unless
C. if
D. after
—How should we deal with air pollution?
—It will be very difficult _____ there are fewer factories and cars.[ ]
A. until
B. unless
C. if
D. after