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: Physiology
[{'content': 'Ghrelin is responsible for: \nSelect and explain. \nA. Stimulation of appetite, B. Suppression of appetite, C. Stimulation of sleep, D. Suppression of sleep', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Stimulation of appetite', 'role': 'assistant'}]