All but Which of the Following Statements About Families and Research

All but which of the following statements about families and research on families is true?

A) families are a key social institution in all societies
B) there has been a substantial amount of research on families within gerontology
C) gerontological research on families is proportionate to research on families in other social science disciplines
D) gerontology researches families in particular because of a focus on caregiving
E) it is not easy to capture, for empirical purposes, what a family is or is not