What calendar is the Chinese zodiac based on?

The Chinese zodiacs are based on a twelve-year cycle, each year in that cycle related to an animal sign. It is calculated according to Chinese lunar calendar.

onto a large boat, and mark the water level that the boat sinks to. then, take the elephant out and put a bunch of marked weights onto the boat until it reaches the same water level. add up the masses of the weights to get the weight of the elephant.

i would think its c but i'm not sure