Why do you think ______ cut down the big tree？
| A．we can't | B．can't we | C．that we can't | D．that can't we |
17..In the United States, bus travel doesn't cost much as train travel, ?
18.
| A．don't they | B．does it | C．do they | D．doesn't it |
19..Someone is at the door, who is_________?
20.
| A．this | B．that | C．it | D．He |
21.—It is raining cats and dogs.
22. — ..
23.
| A．So it is | B．So is it | C．Neither it is | D．Neither is it |
19.—My home is in that tall building over there.
— ?
| A．Can it see | B．Can see it | C．Can be seen it | D．Can it be seen |
20. _________raining hard for 3 hours without stopping.
21.
| A．It is | B．It was | C．It has been | D．It had been |