Final answer:
Marcia's theory on adult identity formation includes both crisis and commitment, which are integral parts of developing a clear sense of self during the growth into adulthood.
Step-by-step explanation:
Marcia argued that adult identity formation involved both crisis and commitment. This concept stems from the work of Erik Erikson, who created a theory of psychosocial development across various stages of life. In the context of adulthood, the establishment of a clear identity is a central developmental task and can entail periods of exploration or crisis, where an individual considers different paths and roles. The process also involves commitment, where an individual makes a choice and invests in certain roles, values, and beliefs, contributing to their identity formation. As such, the correct answer to the question is c) Both crisis and commitment.