How did Incan innovations impact their maintenance of control over a vast empire?

The correct choice highlights how Incan innovations, particularly in infrastructure, significantly bolstered their ability to maintain control over a vast empire. The Incas developed an extensive and sophisticated network of roads, bridges, and communication systems, which facilitated efficient movement of resources, troops, and information across their territory. This infrastructure allowed for swift responses to local unrest, strengthened administrative control, and promoted trade among different regions.

By integrating diverse groups within the empire through trade and communication, the Incas were able to create a sense of unity and shared purpose, thereby reinforcing their authority. The promotion of trade connections also helped in the economic prosperity of the empire, as resources could be exchanged and distributed more effectively, directly linking the well-being of the subjects to the stability of the Incan rule.

Other options, while they may reflect certain aspects of governance or societal structure, do not capture the essential role that trade and communication played in consolidating Incan power across their extensive empire.