`2.` Whose dining room is this? 

`-` It’s their dining room. 

`3.` Whose teacher is this?

`-` It’s our teacher. 

`4.` Whose cats are these?

`-` They’re their cats.

`@@@@@`

`-` Whose + N số ít + is this ?

`-` Whose + N số nhiều + are these ?

`-` It’s + adj sở hữu + N