Turn these verbs into nouns

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Across
  1. 4. signify =
  2. 5. create =
  3. 7. achieve =
  4. 10. assess =
  5. 11. assume =
  6. 12. evaluate =
  7. 13. distribute =
  8. 19. identify =
Down
  1. 1. define =
  2. 2. approach =
  3. 3. specify =
  4. 6. respond =
  5. 8. implicate =
  6. 9. explain =
  7. 11. authorise =
  8. 14. require =
  9. 15. predict =
  10. 16. indicate =
  11. 17. investigate =
  12. 18. evolve =