Ответ:

1. Is that your book? 

2. That's not my ball.

3. They know our friends, but we don't know theirs. 

4. Bob has got a dog but I don't know its name.

 5. These books are mine but this newspaper is yours. 

6. My hands are dirty.

 7. I gave her my address.

Ответ:

1)(your) pen

2)(not my) ball

3)(our) friends.(their)

4)(their)

5)(my)-(your)

6)(mine)

7)(my)