Final answer:
The supplementary motor area (SMA) increases activity during later stages of learning for a well-practiced sequence of finger movements.
Step-by-step explanation:
The correct answer is c. the supplementary motor area increases activity.
The supplementary motor area (SMA) is responsible for planning and coordinating movement, particularly during learned movements. As someone becomes more practiced in a sequence of finger movements, the activity in the SMA increases.
For example, when driving a car, the SMA helps prepare the body for the movements required, such as anticipating a traffic light changing. The premotor area aids in controlling core muscle movements for maintaining posture during movement, and the cerebellum is involved in motor coordination but is not specifically mentioned in relation to increased activity during later stages of learning for a practiced sequence of finger movements.