Final answer:
The frontal lobe continues to undergo enormous changes in adolescence.
Step-by-step explanation:
The correct answer is d) Frontal. While our brains are mostly fully developed by adolescence, the frontal lobes continue to undergo enormous changes. The frontal lobe is responsible for reasoning, motor control, emotion, and language. It contains the motor cortex, prefrontal cortex, and Broca's area, which are all involved in various cognitive functions.