写出下列名词的复数形式。 1. map ________________ 3. church ________________ 5. hero ________________ 7. leaf ________________ 9. tooth ________________ 11. boat ________________ 13. photo ________________ 15. factory ________________ 2. dish ________________ 4. boy ________________ 6. radio ________________ 8. foot ________________ 10. box ________________ 12. dress ________________ 14. potato ________________ 16. mouth ________________