One word substitution

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Across
  1. 2. A person who repairs vehicles
  2. 4. A person who travels to explore new places
  3. 8. A place where books are kept
  4. 9. A person who loves books
  5. 10. A person who can speak two languages
  6. 13. A person who sells medicines
  7. 16. A person who studies the stars and planets
  8. 17. A person who designs buildings
  9. 18. A person who studies history
  10. 20. A person who saves lives at sea
Down
  1. 1. A person who takes photographs
  2. 3. A speech made without preparation
  3. 5. A person who writes for newspapers
  4. 6. A person who works in politics
  5. 7. A person who draws maps
  6. 11. A place where ships are kept
  7. 12. A place where animals are kept
  8. 14. A person who rules a kingdom
  9. 15. A person who writes poems
  10. 19. A person who acts in plays or films