The third option best explains the most crucial element of each civilization:
"The Roman Republic's senate and assemblies were crucial for decision making. The Inca Empire's administrators helped the king keep order and law in different territories, no matter how large the empire was. The Mayan civilization had city-states that were less centralized than either the Republic or Inca Empire."
This option highlights the key components of governance and social organization in each civilization, emphasizing the importance of their respective systems in maintaining order and decision-making processes.