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
Chronic arsenic poisoning 
Select and explain. 
A. Surest sign of identification, B. Probable sign of identification, C. Presumptive sign of identification, D. Doubtful sign of identification
A: Surest sign of identification
Answer: A: Surest sign of identification 
Explanation: Surest sign of identification