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: Ophthalmology
[{'content': 'Brown skin cornea is seen in: \nSelect and explain. \nA. Siderosis, B. Mustard gas exposure, C. Chalcosis, D. All', 'role': 'user'}, {'content': 'Answer: D \nExplanation: A i.e. Siderosis; B i.e. Mustard gas exposure; C i.e. Chalcosis', 'role': 'assistant'}]