问题

Air pollution is getting more and more serious，so we must take action________it is too late.

A:before
B:after
C:until
D:when

正确答案是：

同类题型

other good students, theteacher thinks,

Do you think the phone is genuine—I don’t think it________be a fake，as this shop has a very good reputation.

What happened to him —He was murderlast week.

None knows if _______ that boy, but if _______ him, her parents will be disappointed.

How long will it be ________ the 30th Olympic Games is held in London? —It won’t be two years, I think