Are you up for the challenge?

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Across
  1. 3. Small unit of matter
  2. 4. Person who fights fires
  3. 7. Flying mammal
  4. 9. Physical parts of a computer
  5. 12. Hottest season
  6. 13. Light from the sun
  7. 15. Small fruit that grows in bunches
  8. 17. Force that pulls objects down
  9. 18. Sport played over a net
Down
  1. 1. Something that needs an answer
  2. 2. Common road vehicle
  3. 5. Has a very long neck
  4. 6. Object that attracts some metals
  5. 8. Very dry region
  6. 10. Man's best friend
  7. 11. Removes pencil marks
  8. 13. Long animal with no legs
  9. 14. Organ used for seeing
  10. 16. Natural hole in the ground