The correct answer is (d) At the feet
To explain I would say: Peripheral neuropathy is a disease that mostly affects the peripherals of the body, like the palms or feet. The nerves have faced some sort of trauma or some damage which results in pain, numbness and tingling sensations. These symptoms are mostly expressed at the feet or at the palms so if the doctor suspects peripheral neuropathy at the legs, feet is where they will choose to put the electrodes.