2. by the time we got on the train somebody had taken the last seat. the last seat 3. do they speak italian in switzerland? is 4. they are not re-building the high street until the end of the year. the high street 9. people of all ages can play this game. this game 10. a large crowd was watching the match. the match

Ещё пересмотрю:

1. You can’t feed a cat on dog food.  
A cat can't be fed on dog food.  

2. By the time we got on the train somebody had taken the last seat.  
The last seat had been taken by somebody.  

3. Do they speak Italian in Switzerland?  
Is Italian spoken in Switzerland?   

4. They are not re-building the High Street until the end of the year.  
The High Street is not being re-built until the end of the year.    

5. Was anybody looking after the baby when he fell off the chair?  
Was the baby looked after when he fell off the chair?     

6. Has anybody opened this bottle of mineral water?  
Has this bottle of mineral water been opened by anybody?  

7. Somebody will pick you up from home and take you to the match.  
You will be picked up from home and taken to the match.    

8. Mary had taken the books back to the library.  
The books had been taken by Mary back to the library.      

9. People of all ages can play this game.  
This game can be played by people of all ages.   

10. A large crowd was watching the match.  
The match was watched by a large crowd. 

В пассивном залоге какого-то континьюса нет.
По-моему сейчас правильно.