问题

Every possible means ________ to prevent the air pollution，but the sky is still not very clear.

A:were using
B:have used
C:has been used
D:was used

正确答案是：

同类题型

ly appreciate____ to help me with my maths, butI’m afraid that I have no time this week.

______ nearly all behavior is learned behavior is a basic assumption ______ has been put forward by the social scientists

When everybody was the ship sailed.[ ]

What’s the matter with the man hanging his head there?—Well，if you ________ know, he was caught stealing my bike.

Mrs Smith eats ___________ meat， so she is ___________ fat now