The correct option is C Assassin
'A person who kills somebody especially for political reasons' is Option C, Assassin. Option A, 'Criminal' is a person who has committed crime. Option C, 'Murderer' is someone who illegally or kills another person. Option D, 'Hangman' is a person whose job is to . Thus, options A, B and D are incorrect and the correct word for the given phrase is Option C, Assassin.