III. Put in the right form of pronoun.
1. Don't take … (my/mine) pen! Take … (your/yours)!
2. What was … (your/yours) mother doing?
3. … farm is as rich as … (our/ours/their/theirs).
4. This office is … (their/theirs).
5. Those are Victor's books. The books are … (mine/his/hers).