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': 'All of the following intraocular foreign bodies produce suppurative reaction except: \nSelect and explain. \nA. Pure zinc, B. Mercury, C. Copper alloys, D. Nickel', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Copper alloys', 'role': 'assistant'}]