1. Did he run off with theirs or ours?
2. If he lends us his racquets, we will lend him our ball.
3. Whose big black car is that over there (in the background)? It's Peter's.
4. This book is not yours, it is mine.
5. He traveled with them for a month during vacation 2 years ago.
je ne suis pas sûr si le 1 est correct.