What methods did the Incas use to unify their large empire?

A. they built restaurants in the middle fo thecity so everyone could eat together
B. they created a post office so people could mail letters and stay in touch
C. they developed an extensive road and bridge system throughout the empire to make trade and travel easier
D> they were not able to unify their large empire

C. they developed an extensive road and bridge system throughout the empire to make trade and travel easier