I would say that Brutus' inner struggle with assassinating Caesar is not an example of external conflict, because it is an internal conflict.
External conflicts happen when the character has a conflict with something outside of himself. Often these conflicts are versus another character, nature, or society. If something is not an external conflict, it is an internal conflict. An internal conflict is a problem the character has with himself. The struggle Brutus has with assassinating Caesar is an internal conflict and therefore not an example of external conflict.
symbolism is the correct answer
The answer is symbolism, i just took the test !!
The conflict for power is evident, because it was through him that Caesar lost his life. Symbolic conflict occurs in moral paradoxes, especially in what concerns loyalty and patriotism. The conflict of friendship is evident in the events leading to the pinnacle of history.
So what remains is a class conflict, which is not the target of the piece.