Final answer:
The correct answer is option 1) Personal fable.
Step-by-step explanation:
According to David Elkind, a prominent form of adolescent egocentrism is the Personal fable.
The concept of Personal fable is one where adolescents believe themselves to be unique and protected from harm, which can lead to risky behaviors due to a sense of invincibility. It's different from imaginary audience, where teens feel that they are constantly being watched and judged by others, which is also a form of adolescent egocentrism. On the other hand, identity diffusion and intimacy vs. isolation are Erik Erikson's concepts, with the former relating to adolescence and the latter to early adulthood stages of psychosocial development.
Identity diffusion occurs when an adolescent has not yet achieved a true sense of identity, leading to confusion about the future. Intimacy vs. isolation is a stage in early adulthood where the main concern is developing intimate relationships with others, following a strong sense of self developed in adolescence.