You are answering a USMLE-style medical question. Question: A 49-year-old man comes to the physician because he has had multiple falls and multiple episodes of dizziness over the past 6 weeks. There is no personal or family history of serious illness. He drinks one pint of rum daily. He works as a foreman in a factory that produces industrial solvents. He is alert and oriented to time, place, and person. His temperature is 36.7°C (98.1°F), pulse is 88/min, and blood pressure is 108/70 mm Hg. Examination shows a wide-based gait. The patient is unable to stand with his feet together without support. There is a coarse tremor of the hands when he is asked to grab a pen. Muscle strength and tone are normal in all extremities. Sensation to pain, vibration, and position is intact bilaterally. Rapid alternating movements of the hands is impaired. Mental status examination shows no abnormalities. Which of the following is the most likely cause of this patient's condition? Options: A) Korsakoff syndrome B) Methanol poisoning C) Cerebellar degeneration D) Wernicke's encephalopathy Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.