the answer is: B. reality principle; ego
According to Sigmund Freud, ego is the ideal perception that we want other people to see. Primal urges that we have often opposed the social norms that imposed within the society around is. Ego is the tool that we have to control these primal urges so it does not violate the norm.
The problem with this is that fulfilling our primal urges felt so satisfying. Because of this, in order to maintain our ego we need away to delay our gratification. The efforts that we made to do this is what we call as reality principle.