The assumption of families exist in all societies derives from a study of G. P. Murdock. Murdock, a functionalist anthropologist, examined 250 societies in a wide range including both hunting and gathering societies and industrial societies. He concluded that a form of family exists in every society, thus the family is a universal social institution. For Murdock, the family is also a social group characterized by common residence, economic co-operation and reproduction. It includes adults of both sexes, at least of whom maintain a socially approved sexual relationship, and one or more children, own or adopted, of the sexually cohabiting adults. The correct answer is E.