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: Medicine
[{'content': 'Most common cause of Cushing syndrome is \nSelect and explain. \nA. Pituitary tumor, B. Ectopic ACTH producing tumor, C. Steroid supplementation, D. Adrenal tumor', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Steroid supplementation is the most common cause of question syndrome.', 'role': 'assistant'}]