Final answer:
Marriage to a partner from the same social group or caste is referred to as endogamy. The correct option is C.
Step-by-step explanation:
Marriage limited to partners who are members of the same social group or caste is referred to as endogamy. This is in contrast to exogamy, which is a union between spouses from different social categories. Societies often have norms (endogamy rules) that encourage individuals to marry within certain groups such as the same generation or linguistic group.
However, they may marry outside of certain groups, for instance, not marrying within very close kin, as addressed in exogamy rules. Rules of incest are also established to define which relationships are considered too close for marriage.