Тоже хвостики : ) there isn't a sandwich in the box, the browns wanted to have lunch at home , ? there isn't a mouse in the house , the greens are watching tv , ? the greens watch tv in the evening , the greens watched tv yesterday

There isn't a sandwich in the box, is there? the browns wanted to have lunch at home, did't they? there isn't a mouse in the house, is there? the greens are watching tv, are't they? the greens watch tv in the evening, don't they? the greens watched tv yesterday,    didn't they?

There isn't a sandwich in the box, is there? the browns wanted to have lunch at home, did't they? there isn't a mouse in the house , is there? the greens are watching tv , are't they? the greens watch tv in the evening , do't they? the greens watched tv yesterday,    did't they?

2) they are still excavating the site of china’s northern province.

the site of china’s northern province is still being excavated

3)) they'll not deliver the parcel tomorrow.

the parcel will not be delivered tomorrow

4) she has cancelled this meeting.

the meeting has been cancelled by her

5) he stole my wallet.

my wallet was stolen by him

6) t. shevchenko painted “a peasant family”.

“a peasant family” was painted by t.shevchenko

7) we encourage visitors to our heritage sites.

visitors are encouraged to the heritage sites

8) they completed the monument in 1648.

the monument was completed in 1648

9) four domed chambers surround the taj.

taj is surrounded by four domed chambers

10) twenty thousand workers built the taj mahal entirely of white marble

taj mahal was build entirely of white marble (by twenty thousand workers)

дополнение: "by them" писать бессмысленно, не важно кто это - они. для этого и полезен passive

ответ:

1.do you often travel by plane?

yes,i often travel by plane.

2.did you travel by train last summer?

no,i didn't travel by train last summer.

3.does your mum go to work by bus?

yes,my mum go to work by bus.

4.have you got a bicycle?

no,i don't have a bicycle.

5.has your dad got a motorbike?

no,my dad don't have a motorbike.

6.can you drive a car?

no,i can' drive a car.

7.can you ride a bicycle well?

no,i can't ride a bicycle well.

8.do you want to travel with your friends?

yes,i want to travel with my friends.