Is this his T-shirt?
No, it isn't.
What is this?
This is a ... / It is a ...
What are these?
These are ...
This is ___ dress.
her
What are these?
These are ...
Is this her dress?
Yes, it is.
Are these his shorts?
Yes, they are.
These are ___ socks.
her
This is ___ T-shirt.
his
What is this?
This is ... / It is ...
What are these?
These are ...
Are these her trousers?
No, they aren't.