Answer:
The answer is c. A caste system.
Explanation:
This system, very prominent in India, is based on castes: this is, a social structure characterised by the hereditary transmission of values and traditions, which include occupation, lifestyle and beliefs. Castes might exclude different social groups based on the concept of "purity" and "pollution".
This means that the lower castes are unlikely to advance economically, especially since caste systems are based on endogamy (marrying only people in the same class or ethnic group).