This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Inorganic Irritants, Subject name: Forensic Medicine
[{'content': 'In a suspected case of death due to poisoning where cadaveric rigidity is lasting longer than usual, it may be case of poisoning due to \nSelect and explain. \nA. Lead, B. Arsenic, C. Mercury, D. Copper', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e. arsenic Arsenic poisoning delays rigor mortisAlso rememberRigor is delayed by cold and accelerated by heat*Rigor mortisCommences in about 2-3 hrs*Develops in-12 hrs*Persists for-12 hrs*Passes off -12 hrs*More questions on Rigor mortisRigor mortis first appears in involuntary muscles and then in voluntary muscles.*First involuntary muscles to be involved in rigor mortis - heart muscles*First voluntary muscle to be involved in rigor mortis - Muscle of eyelid*", 'role': 'assistant'}]