Final answer:
Plato and Aristotle did not explicitly define 'adolescence,' but their ideas on youth development suggest they saw it as a transition from childhood to adulthood.
Step-by-step explanation:
Plato and Aristotle did not define adolescence in the way we understand it today. The concept as we know it—a period of transition between childhood and adulthood characterized by rapid physical growth, cognitive development, and psychosocial changes—was not explicitly discussed by these philosophers in such terms. However, we could infer their views on the subject through their ideas on education and human development. For the purposes of the student's question, the closest answer within the context of classical philosophy's views on youth development could be (d) as a transition from childhood to adulthood, given that both philosophers discussed youth as a stage of development leading to the completion and fulfillment of a person's capabilities.