What was the significance of a 52 year cycle in both the Aztec and the Mayan calendars?

a. That was the average lifespan of a Mayan or Aztec individual.
b. The ritual and agricultural cycles finished together every 52 years.
c. Mesoamericans used a base-13 instead of base-10 number system.
d. A Mesoamerican myth said that the sun was reborn every 52 years.