The Taboo of Incest Was Believed to Have Developed

The taboo of incest was believed to have developed

A) due to the fear that close inbreeding would produce abnormal offspring
B) because people who live together constantly develop a sexual aversion to each other
C) because the family cannot tolerate the ambiguity or blurred role definitions brought about by the sexual involvement of family members with each other
D) all of the above were theories but the current theory was that it was due to the need for barter among peoples
E) none of the above