Final answer:
The incest taboo is a universal cultural norm against close-relative sexual relations, and one explanation for it is the avoidance of inbreeding, which can result in harmful genetic consequences.
Step-by-step explanation:
The universal incest taboo is a social norm found across various cultures that prohibits sexual relations between close relatives, including between parents and their offspring. One of the explanations for this taboo has been identified in the theory of kin selection, which suggests that helping close relatives can increase the chances that one's genes will be passed to subsequent generations. Another explanation cited by functionalists relates to the necessity of regulating sexual activity to ensure the stability of the family unit and the provision of resources for offspring.
Concerning the provided options for explaining the incest taboo, the closest option would be 'C', which states that inbreeding would lead to the expression of bad genes. Inbreeding can result in the congregation of deleterious mutations, leading to harmful phenotypes. This biological perspective on avoiding the negative consequences of inbreeding can be viewed as a key component in the rationale behind the incest taboo.