【单选题】

One of the most significant elements of age stratification in all cultures is the pattern of experiences connected to marriage and parenting--a pattern that sociologists call the family life cycle. In NorthAmerica, about 90 percent of adults marry, and the great majority of them have children and thus a family life cycle related to family experiences. When the family’s first child is born, the parents embark on a sequence of experiences linked to the child’s development--from infancy and toddlerhood, through school age and adolescence, and eventually, to departure from the nest.Each of these periods in the child’s life makes a different set of demands on the parents.

It can be inferred from the passage that the family life cycle
A、takes place whether or not people have children
B．does not occur in cultures outside of NorthAmerica
C．must be redefined from one generation to the next
D．shapes several years in the lives of most adults