The correct answer is D, as the moment in Oedipus the King where Oedipus realizes he killed his father and married his mother is called the anagnorisis.
Anagnorisis is a narrative resource that consists in the discovery by a character of essential information about his identity, his loved ones or his environment, hidden for him up to that moment. The revelation alters the behavior of the character and forces him to get a more accurate idea of himself and his surroundings. Anagnorisis also occurs when a main character reveals his identity until then hidden or veiled to other secondary characters thus changing the relationship, usually from a weak or non-existent link (a beggar or simple guest) to a strong link (the son of an enemy who claims vengeance, the return of a long-absent king, etc ...), producing a turning point in the story that makes it move towards its outcome.
A classic example of anagnorisis in the Greek tragedy is found in "Oedipus the King" of Sophocles, when Oedipus learns that the person he had killed was his father and that his wife is his mother.