What were the four social groups of ancient Persia outlined by Al-Biruni in order to explain what he really meant to say?

Ans. By seeking for analogies in other civilizations, Al-Biruni attempted to explain the caste system. He said that there were four social classes in ancient Persia. There were kings and princes among them, as well as monks, fire priests, and attorneys, as well as doctors, astronomers, and other scientists, peasants, and craftsmen.