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': 'Which of the following has growth hormone stimulating activity? \nSelect and explain. \nA. IGF-1, B. Somatostatin, C. REM sleep, D. Ghrelin', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]