Final answer:
The conspirators want Brutus to join them because his respect among the people would lend credibility to the assassination of Caesar, making it seem like a noble act. The correct option is c.
Step-by-step explanation:
The conspirators think it is important for Brutus to join them because Brutus is well-respected by the Roman people. The respect Brutus commands among the populace would lend credibility and honor to their cause, potentially helping to stabilize Rome after the planned assassination of Julius Caesar.
They believe that with Brutus on their side, it would appear less like a power grab and more like a noble act for the republic, particularly because Brutus is known for his stoic and virtuous personality, which aligns with Roman values. The correct option is c.