What Particular Aspect of Life in Industrial Nations Makes the Nuclear

What particular aspect of life in industrial nations makes the nuclear family practical?

A) The emphasis on relations with kin outside the nuclear family serves to link the otherwise isolated nuclear family with kin that may be economically helpful.
B) Family isolation arising from geographic mobility and living where jobs are available means that most middle-class couples, much like foraging people, establish households and families of their own.
C) A strong form of individualism has arisen in middle class American culture that conflicts with life in larger family groups.
D) When some poor people escape the poverty often associated with industrial societies, they no longer feel obligated to provide financial aid to the circle of less fortunate relatives, breaking off relations with their family and starting their own household.
E) Neolocality is the traditional form of residence in most societies, established long before societies became industrial and persisting long after.