Final answer:
d) Identity achievement. The behavior described in the question best aligns with the concept of identity achievement in adolescent development.
Step-by-step explanation:
The behavior described in the question best aligns with the concept of identity achievement in adolescent development. Identity achievement occurs when individuals have successfully explored various options and have made a commitment to an identity that feels authentic to them. Kiara confidently stating that she wants to be a doctor demonstrates a clear sense of identity and commitment to a future career.