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: Surgery
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. Oleander, D. Sodium nitrite
B: Hydrogen sulphide
Answer: B: Hydrogen sulphide 
Explanation: Colour of post-moem staining in poisoning- 1) Dark brown or yellow- Phosphorus or acute copper poisoning, 2) Cherry red- CO & Cold storage, 3) Bluish-green- H2S, 4) Bright red- HCN/ Cyanides, 5) Chocolate/Red-brown coloured- Nitrites/Nitrates, aniline, Nitrobenzene, Acetanilide, Bromates, Chlorates (due to formation of Metahemoglobin.)