This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
[{'content': "In addison's disease, most diagnostic test is - \nSelect and explain. \nA. Serum Na+, K+, renin, B. S. Na+, K+, saline suppression, C. Serum creatinine\\/urea ratio, D. ACTH stimulation test", 'role': 'user'}, {'content': 'Answer: D \nExplanation: to assess adrenal reserve capacity for steroid Production ( Harrison 17 pg 2264)', 'role': 'assistant'}]