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': "Surest sign of brain stem death \nSelect and explain. \nA. Absent Doll's eye reflex, B. Fixed dilated pupil not reacting to light, C. Cheyne Stokes breathing, D. Decerebrate posture", 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Fixed dilated pupil not responding to light Cooling of body & rigor mois is a sign of molecular or cellular death. - Somatic (systemic, clinical or brain) death is cessation of spontaneous breathing, circulation and brain activity (as indicated by flat isoelectric EEG, deep unconsciousness with no response to external stimuli or internal need). Surest sign of brain stem death is fixed dilated pupil not constricting (responding) to light.Q', 'role': 'assistant'}]