According to Levinson,

life structures prepare the adult for the next transition.

transitions occur at the beginning of each era or stage.

structures are highly similar for all individuals.

transitions arise only in circumstances of stress and trauma.

Answer: transitions occur at the beginning of each era or stage.

Explanation:

In Daniel Levinson's comprehensive theory of adult development, there are 6 stages of adulthood, known as the Seasons of a Man's Life: Early adult transition (17-22), Entering the adult world (22-28), Age 30 transition (28-33), Settling down (33-40), the Mid-life transition (40-45), and Entering middle adulthood (45-50). In this model, there's a stable period in which people make fundamental life decisions, and the Transitional Period, when we come to the end of a stage and start a new one.