6th review

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Across
  1. 3. frozen water
  2. 4. found in the immune system
  3. 8. gas exchange
  4. 9. where planes fly
  5. 13. makes proteins
  6. 15. explains why
  7. 16. outer layer of a planet cell
  8. 17. variable that you change
  9. 18. where we live
  10. 19. break down food into nutrients
  11. 20. changes rapidly
Down
  1. 1. makes ATP energy
  2. 2. air
  3. 5. long period of time weather
  4. 6. repeating an experiment multiple times
  5. 7. responsible for movement
  6. 10. water
  7. 11. has meteors
  8. 12. holds the DNA
  9. 14. part of the nervous system