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': 'All are causes of sideroblastic anaemia, except \nSelect and explain. \nA. Collagen vascular disease, B. Iron deficit, C. Lead poisoning, D. Cutaneous porphyria', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]