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': 'Fish liver oil is the richest source of: September 2006 \nSelect and explain. \nA. Vitamin K, B. Vitamin E, C. Vitamin D, D. Vitamin A', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D: Vitamin A Fish liver oil is the richest source of vitamin A, but they are used as nutritional supplements rather than as food sources.', 'role': 'assistant'}]