This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Drowning, Subject name: Forensic Medicine
[{'content': 'The outer covering of diatom is made of: \nSelect and explain. \nA. Magnesium, B. Silica, C. Hydrocarbons, D. None', 'role': 'user'}, {'content': 'Answer: B \nExplanation: MEDICO-LEGAL SIGNIFICANCE OF DIATOMS TEST Diatoms are unicellular algae with silicaQ***in its cell wall Only a beating hea can transpo the diatoms to distant organs It indicates death due to drowningQ*** Diatoms in bone marrow and brain is more reliable than any other organ As diatoms resist putrefactionQ***, it is valuable even in putrefaction Diatoms are negative in dead bodies thrown in waterQ***or dry drowningQ***', 'role': 'assistant'}]