Answer:
little headway, would be a good synonym for little progress
Honestly I would choose A.
Cassius wants Brutus to join the conspiracy because he knows that Brutus is an influential person and the people love him.
If they can get as many respectable people on their side, then the deed they have planned will seem acceptable to the people (or so they think).
I would say that the sentence which uses a vocabulary word wrong is C) The melancholy scene brought a chill cadence to the back of my neck.
Cadence is a rhythm, or a sequence of notes.