一、單項選擇(每小題1分，共15分)

1、Every possible means____to prevent the air pollution. But the sky is still not clear.

A. is used

B. are used

C. have been used

D. has been used

2、John shut everybody out of the kitchen______he could prepare his surprise for the party.

A. which

B. when

C. so that

D. as if