Final answer:
The correct answer to the question about the secondary motor area hidden on the medial surface of each hemisphere, responsible for initiating movement, is b) Supplementary Motor Area.
Step-by-step explanation:
The secondary motor area that is just dorsal to the premotor cortex and is largely hidden from view on the medial surface of each hemisphere is the Supplementary Motor Area. This area is responsible for initiating movements by directly connecting to cranial and spinal motor neurons. It is also involved in planning and coordinating movements, including the management of sequential movements that are based on learned behaviors. While the prefrontal cortex is involved in executive functions, judgment, and abstract reasoning, and the occipital lobe is associated with visual processing, neither of these areas fits the description provided. The postcentral gyrus is instead related to sensory processing, hence not the right answer. Therefore, the correct answer to the provided question is b) Supplementary Motor Area.