This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Retina, Subject name: Ophthalmology
[{'content': 'Which of the following foreign body can not be observed as such in retinal coats and need to be removed \nSelect and explain. \nA. Nickel, B. Chromium, C. Aluminium, D. Copper', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ine Materials that can be observed inside eye: Nickel Chromium Aluminium Gold Plastic Copper has toxic potential for the ocular tissues and has to be removed', 'role': 'assistant'}]