Puzzle 81

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Across
  1. 4. The planet with the most gravity.
  2. 6. An element Joseph Priestley discovered.
  3. 7. An inorganic molecule produced by lightning.
  4. 11. The study of the weather.
  5. 15. The bending of a sound or light wave.
  6. 18. A name first used by William Shakespeare.
  7. 19. The tallest type of grass.
  8. 20. The study of light and vision.
Down
  1. 1. The best selling novel of all time.
  2. 2. The quality that allows an object to float on water.
  3. 3. The largest internal organ in the human body.
  4. 5. Malfunction of this organ results in diabetes.
  5. 8. The number of bones in a Shark's body.
  6. 9. The medical term for bad breath.
  7. 10. The subatomic particle with no charge.
  8. 12. The first-ever living creature to be cloned.
  9. 13. A famous ship that sunk in 1912.
  10. 14. The language the name “Australia” is derived from.
  11. 16. The first cash crop in America.
  12. 17. The term for the policy of racial segregation in South Africa.