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: Social & Preventive Medicine
[{'content': 'Which pathway describes the synthesis of metabolically active vitamin D: March 2004 \nSelect and explain. \nA. Liver - skin - kidney, B. Gut - kidney - liver, C. Kidney - liver - skin, D. Skin - liver - kidney', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D i.e. Skin - liver - kidney', 'role': 'assistant'}]