1. A: Whose toys are they? Are they yours?

 B: No, they aren't mine. They are Ted's and Fay's. They are theirs.

2. A: Is this umbrella yours?

 B: No, it's Jerry's.

3. A: There is a nice water bottle under the desk. Whose is it?

 B: It's Sally's.

4. A: Whose sunglasses are they?

 B: They're Ben's.