This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Asphyxia, Subject name: Forensic Medicine
[{'content': 'The outer covering of diagram is made of - \nSelect and explain. \nA. Magnesium, B. Silica, C. Hydrocarbons, D. None', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Reff: The synopsis of forensic medicine & Toxicology 28th edition pg: 195 Cell wall is usually strongly impregnated with silica and contain chlorophyll and diatoms a brown pigment. Diatom secretes hard siliceous outer box like skeleton called frustule. They resist heat and acid', 'role': 'assistant'}]