This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Poisoning, Subject name: Forensic Medicine
A dead body is having cadaveric lividity of bluish green colour. The most likely cause of death is by poisoning due to - 
Select and explain. 
A. Hydrocyanic acid, B. Hydrogen sulphide, C. Ocleander, D. Sodium nitrite
B: Hydrogen sulphide
Answer: B: Hydrogen sulphide 
Explanation: Poison Color Nitrites Reddish brown Potassium chlorate Chocolate brown Phosphorus Dark brown Hydrogen sulphide Bluish green Cyanide Cherry red Carbon monoxide Pink Opium Blackish Ref: K.S.Narayan Reddy's Synopsis of Forensic Medicine and Toxicology, 29th edition, Chapter 35.