SIMPLE PAST - Regular or irregular?

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Across
  1. 4. Simple past COME
  2. 5. Simple past LOVE
  3. 6. simple past BUY
  4. 9. simple past TEACH
  5. 10. Simple past READ
  6. 12. Simple past FEEL
  7. 14. Simple past EAT
  8. 16. simple past SING
  9. 17. Simple past GO
  10. 18. simple past SLEEP
  11. 21. Simple past SWIM
  12. 23. Simple past DRINK
Down
  1. 1. Simple past DO
  2. 2. Simple past SAY
  3. 3. Simple past FORGET
  4. 4. Simple past COOK
  5. 7. Simple past GET
  6. 8. simple past WRITE
  7. 11. Simple past KNOW
  8. 13. Simple past TEACH
  9. 15. Simple past MAKE
  10. 17. Simple past BE
  11. 19. Simple past LOSE
  12. 20. Simple past PLAY
  13. 22. Simple past FIND