John want to be a sociology major who studies the social cause of crime. he is majoring in .

He is majoring in criminology.

Criminology refers to the study of crime, deviance, criminal acts and the penal system. Criminology is a sub-group of both psychological and sociological disciplines. Criminology specifically focuses on the cause, effects, theories of crime and prevention of crime in society. Criminology involves analyzing the human and societal factors that contribute to crime. 

the answer would be C :)