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': '"Orange skin" cornea results due to: \nSelect and explain. \nA. Chalcosis, B. Siderosis, C. Ammonia burn, D. Mustard gas', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. Mustard gas', 'role': 'assistant'}]