B. Him Singing. Such an odd question
In Oedipus rex, sphinx symbolises the Oedipus courage, when Oedipus courageously without being scared of the death accepted the riddle of sphinx. He gave the correct answer of his riddle. Which cause him disappear and he died at that very moment.So it was the courage that caused a great set back to the death.
The answer is D: He doesnt want Lennie to be tempted by her.