challenge: What were calpulli in pre-Columbian Aztec society?
  
  A. Forms of Aztec currency used for trade
  B. Types of temples for religious worship in Aztec cities
  C. Units of commoner housing that had been split into kin-based or other land holding groups within Nahua city-states
  D. Units of noble housing within Nahua city-states
  Answer: 