Final answer:
A caste system is social stratification based on birth and is a closed system with no social mobility, in contrast to class systems and meritocracy which are more open and enable movement based on achievement.
Step-by-step explanation:
A caste system is a form of social stratification where individuals are born into a social status, which they retain throughout their life and cannot change. By contrast, a class system allows for more social mobility as it is open and based on social factors and individual achievement. A meritocracy is an ideal system where status and mobility are based solely on personal effort and merit, but in reality, no pure meritocracy has ever existed.
A caste system is considered a closed system with high status consistency, where there is little to no opportunity to change one's social standing, with positions determined at birth. In contrast, a class system and meritocracy are more open, providing individuals the chance to change their social status through factors such as achievement, wealth, income, and occupation. However, true meritocracy has never been fully achieved, as societies have other determining factors that contribute to social stratification.
In response to the question, c) "based on birth" is the characteristic that defines a caste system, where social stratification is firmly fixed and predetermined by one's birth into a specific social group.