1. invalidate
  2. invalidate oneself
  3. invent
  4. invent oneself
  5. invert
  6. invert oneself
  7. invest
  8. invest oneself
  9. investigate
  10. investigate oneself
  11. invigorate
  12. invigorate oneself
  13. invite
  14. invite oneself
  15. invoice
  16. invoice oneself
  17. invoke
  18. invoke oneself
  19. involve
  20. involve oneself