Final answer:
Robert Havighurst believed that adolescents must complete a series of developmental tasks (A). This aligns with broader societal milestones such as completing school and becoming financially independent, which are being delayed by newer generations like Millennials.
Step-by-step explanation:
Robert Havighurst believed adolescents must complete a series of tasks during their development. These tasks, often seen as developmental challenges, include learning to relate with peers, forming a sense of identity, and preparing for a career. This period is crucial as it is filled with significant transition points where adolescents are socialized into new roles that can vary between societies. For instance, U.S. socialization of high school graduates typically involves expectations to enter college, trade school, or the workforce shortly after graduation, as opposed to other practices such as mandatory military service or taking a gap year seen in other countries.
These developmental tasks set by Havighurst align with the broader concept of social milestones that individuals aim to achieve, like those detailed by Henig which include completing school, leaving home, becoming financially independent, marrying, and having a child. These milestones are increasingly being delayed by generations such as Millennials, raising questions about how future societies will define adulthood. The changes in these milestones and cultural expectations reflect the diverse pathways individuals can take in their journey to adulthood.