Final answer:
Augustus used the title princeps to avoid being seen as a king, to convey his authority and prestige, and to highlight his influence and service to the Republic.
Step-by-step explanation:
Augustus used the title princeps for several reasons. First, he wanted to avoid being perceived as a king, which would have been unacceptable to the Roman people. The title princeps, meaning 'first citizen,' allowed him to maintain the facade of republican rule while consolidating his power as the sole leader of Rome. Second, Augustus used the title to convey his authority and prestige to the Senate and the people, solidifying his position as the leader of the Roman Empire. Lastly, the title princeps Senatus, or 'leader of the Senate,' highlighted his influence and service to the Republic.