____ is the practice that one must marry within one's own caste or group.

Correct option is B

Ans. (b)
Sol. Endogamy is the practice of marrying within one's own social group, caste, or community. This practice is often followed in many societies and cultures where marriage outside one's group is discouraged or prohibited.
Explanation of each option:
· (a) Polygamy – Refers to the practice of having more than one spouse at the same time.
· (b) Endogamy – Correct answer. The practice of marrying within one’s own caste, group, or community.
· (c) Monogamy – Refers to the practice of having only one spouse at a time.
· (d) Quadrigamy – Refers to the practice of having four spouses at a time (which is not a common term).