Final answer:
John's partial blindness is most likely due to damage in the occipital lobe of the cerebral cortex, which is essential for vision. The correct option is c.
Step-by-step explanation:
If John is partially blind due to damage in one of the lobes of his cerebral cortex, the most likely location for his brain's damage is the occipital lobe. The occipital lobe, located at the back of the brain, is primarily involved in vision—seeing, recognizing, and identifying the visual world. Damage to the occipital lobe can lead to visual deficits such as blindness or partial blindness, depending on the extent and location of the damage. Hence, c is the correct option.