ubuntu@linux:~$ gpg --output revoke.asc --gen-revoke  C4DF0614

sec  2048R/C4DF0614 2016-07-23 remonshai (i am mathematics student) <remonshai@gmail.com>

Create a revocation certificate for this key? (y/N) y
Please select the reason for the revocation:
  0 = No reason specified
  1 = Key has been compromised
  2 = Key is superseded
  3 = Key is no longer used
  Q = Cancel
(Probably you want to select 1 here)
Your decision?