The Aztecs succeeded in developing a remarkable urban landscape. The population of Tenochtitlan and Tlatelolco combined with that of the cities and towns of the surrounding lakeshore was approximately 500,000 by 1500 C. E. Three causeways connected this island capital to the lakeshore. Planners laid out the urban center as a grid where canals and streets intersected at right angles to facilitate the movement of people and goods.

Which of the following can be inferred about the Aztecs based on the above passage?
a. The Aztecs had a strong centralized government capable or organizing a large labor force.
b. The Aztecs had a large number of slaves, and efficient techniques to minimize slave rebellion.
c. The Aztecs conquered a pre-existing capital city.
d. The Aztecs had contact with urban planners from Eurasia.