问题

Every possible means _______to prevent the air pollution, but the sky is still not clear

A:are being used
B:have been used
C:has been used
D:had been used

正确答案是：

同类题型

What color is it —It’s ____ blue , it’s ____ blue ruler.

The girl with two cats inthe yard when the earthquake happened.

Here____! Where is Xiao Liu?　 —- There____.

To have a balance between study and a social life I’m going to join a few clubs ______I’ll make some new friends

hy are they taking all the equipmentaway—The job ____, they are packing up toleave.