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
On stomach washing which poison turns to black on exposure to silver nitrate: 
Select and explain. 
A. Tik 20, B. Celphos, C. Malathion, D. Arsenic
B: Celphos
Answer: B: Celphos 
Explanation: B i.e. Celphos