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: Forensic Medicine
[{'content': 'The outer covering of diatom is made of: NEET 14 \nSelect and explain. \nA. Magnesium, B. Silica, C. Hydrocarbons, D. None', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Silica', 'role': 'assistant'}]