Четвёртый лишний.

1. have, 2. when, 3. us, 4. she, 5. it, 6. he, 7. it, 8. them, 9. mine, 10. you, 11. young, 12. slim, 13. name, 14. old, 15. family, 16. baby, 17. Polish, 18. straight.