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
A dead body with suspected poisoning is having hypostasis of red-brown or deep blue in color. It is suggestive of poisoning due to - 
Select and explain. 
A. Nitrates, B. Carbon monoxide, C. Cyanides, D. Barbiturates
A: Nitrates
Answer: A: Nitrates 
Explanation: Reddish brown or chocolate colored or deep blue hypostasis is suggestive of poisoning due to nitrates, nitrites, nitrobenzene, due to the formation of methemoglobin.