Order the following concepts from least to most rigid in terms of social mobility: A) Class System, B) Caste System, C) Meritocracy, D) Ancestry.

To understand social mobility, we can think about how easy or hard it is for people to move up or down in society. In a meritocracy, where people are rewarded based on their abilities and efforts, social mobility is the highest because anyone can succeed if they work hard. Next is the class system, which allows some movement between classes based on factors like education and income, making it somewhat flexible. The ancestry concept is more rigid because it ties social status to family background, limiting movement but still allowing some change. Finally, the caste system is the most rigid because it is fixed by birth, meaning people cannot change their social status regardless of their efforts.