问题

The air pollution is so terrible.–It will be worse we do something to protect the environment.

A:if
B:unless
C:after
D:when;

正确答案是：

同类题型

31. The chair looks rather hard，but in fact it is very comfortable to________.

Leif followed Biarn’s directions and sailed to _______is believed to be the coast of present-day Canada.

_____ realize his dream, he works very hard.[ ]

This party is ______idea! It ‘s exactly what I want .

You seem to like sweets.—_______. That’s probably why I’m becomingfatter and fatter.