Answer: A. Exogamy
Explanation: Exogamy can be simply refered to as the custom or norms of marrying someone outside of your own community, clan or social group. The society normally decides the rules that will govern the marriage as well as the extent of the marriage such that they may agree for it to happen just once or continual marriage between the two communities or clans. This kind of marriage build alliance between the communities and clans as well as reduce the chances of their offspring have a certain kind of diseases which they are trying to avoid.