The third one

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Across
  1. 3. – A dense, tropical forest
  2. 6. – A triangular ancient structure
  3. 7. – A colorful explosion in the sky
  4. 9. – A portable light source
  5. 10. – A vast system of stars and planets
  6. 12. – A container for liquids
  7. 15. – A traveling show with acrobats and clowns
  8. 16. – A machine that can perform tasks
  9. 17. – A staple food made from flour
  10. 18. – The absence of sound
Down
  1. 1. – A visible mass of condensed water vapor in the sky
  2. 2. – A large striped wild cat
  3. 4. – A sailor who steals on the seas
  4. 5. – A device used to take pictures
  5. 6. – A celestial body orbiting a star
  6. 7. – A fast-flying bird of prey
  7. 8. – The largest mammal in the ocean
  8. 11. – A heavy object that holds a ship in place
  9. 13. – A tool used for climbing
  10. 14. – A device used for heating