一台局部通风机最多只能向2个掘进工作面供风。

把下列句子变成反意疑问句。

1. We can't wait for them any longer, __________?

2. The weather here isn't very old, __________?

3. There is a tree in front of the building, _________?

4. Your brother doesn't enjoy playing football, __________?

5. This Saturday is Children's Day, __________?

6. Jim had his lunch at the factory, __________?

7. Ann and her parents live in the country, __________?

强制许可制度只适用于发明专利和实用新型专利。

自由膨胀率δ_ef（）的土为中膨胀土。

A.65％≤δ_ef＜80％

B.55％≤δ_ef＜80％

C.65％≤δ_ef＜90％

D.55％≤δ_ef＜90％

旅客的出行目的不同，其需求价格弹性也不同，一般认为( )旅客的需求价格弹性最低。

A．公务
B．旅游
C．探亲访友
D．求学