Step 1: Understanding the concept of prohibition regarding marriage.
The term "incest taboo" refers to the social and cultural prohibition of sexual relationships and marriage between close relatives, typically within the family. It is a universal norm in most societies that restricts marriage between individuals who are too closely related.
Step 2: Understanding endogamy and exogamy.
Endogamy refers to the practice of marrying within a specific group, community, or social class, while exogamy is the practice of marrying outside one's group. Neither of these is a prohibition but rather a practice related to marriage patterns.
Step 3: Conclusion.
The prohibition regarding marriage is best represented by the incest taboo, as it specifically restricts certain marriages based on close familial relationships.
Final Answer: \[ \boxed{\text{The correct answer is (C) Incest taboo.}} \]