This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'In prolonged starvation the main energy source of brain is: \nSelect and explain. \nA. Glucose, B. Ketone bodies, C. Fructose, D. Fatty acids', 'role': 'user'}, {'content': 'Answer: B \nExplanation: STARVE FEED CYCLE\nDivided into 5 stages:\n\nWell-fed state (1–4 hours after food)\nEarly fasting (4–16 hours after food)\nFasting (16–48 hours after food)\nStarvation (2–3 days without food)\nProlonged starvation (> 5 days without food).', 'role': 'assistant'}]