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
In a suspected case of death due to poisoning where cadaveric rigidity is lasting longer than usual, it may be a case of poisoning due to - 
Select and explain. 
A. Lead, B. Arsenic, C. Mercury, D. Copper
B: Arsenic
Answer: B: Arsenic 
Explanation: Cadaveric rigidity is delayed and therefore appears for long in arsenic poisoning.