Final answer:
The family life course theory is chosen by family theorists to study long-term developmental trajectories and transitions in families. It recognizes that family events occur in a fluid course rather than in strict stages.
Step-by-step explanation:
The family life course theory is often chosen by family theorists when they want to study long-term developmental trajectories and transitions in families. Unlike traditional stage theories, the family life course model recognizes that family events occur in a fluid course rather than in strict stages. This allows for the exploration of changes in family structure and dynamics over time, including shifts in marriage patterns, childbearing outside of marriage, and other societal shifts in family life.