Both the mayo and the Aztec had two , one for religion and one for farming

radioactive dating, also known as  radioisotope dating  is a process that in  estimating the approximate  age  of  rocks. these data can be analyzed from  the studies dealing with the  decay of the radioactive elements that are present in these rocks. in nature, there are a few types of materials or atoms which are quite unstable and they spontaneously decay or breakdown to form other kinds of atoms.

definitely a for sure. ill see and update if i get the answer

the crusaders are identified in the painting;

c. by the red crosses on their backs