To What Does Does "Virtual Families" Refer

To what does does "virtual families" refer?

A) Those empowered by law to care for their family members, i.e. children, old people and the severely ill.
B) Those people who do the actual work of caring for family members, such as grandparents, aunts, uncles, cousins, friends or neighbours.
C) Those family members who share the same last name.
D) The new family a woman joins when she marries into her husband's family.