Answer is D. Lucilius gives Brutus information about Cassius, which influences Brutus's judgement of Cassius.
When Brutus asks Lucilius about how Cassius received him, Lucilius answered that he was not as friendly as always. This made Brutus reflect on the kind of friend Cassius is, explaining Lucilius that this is the way a false friend behaves. In the end, Brutus advised him he should no longer rely on a person like this.
