Fill in the boxes

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Across
  1. 1. Made of short bones
  2. 5. Made of long bones
  3. 6. Prevents us from getting ill
  4. 9. Made of irregular bones
  5. 10. Made of flat bones
Down
  1. 2. Animals without a backbone
  2. 3. Particles are tightly packed
  3. 4. Making the environment dirty
  4. 7. Signs of illness
  5. 8. Particles are far apart