—Could I smoke here?—I’d prefer _______if you don’t smoke in front of the children.

The CDs are on sale!Buy one and you will get___________completely for free．

–What do you think of the lecture?--____but interesting, but I’ve managed to survive it.

Days in winter are shorter than ___ in summer.

 ---Which book could I take? ---Oh, you can take ____of them. I’ll keep none.