This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Death and postmortem changes, Subject name: Forensic Medicine
Surest proof of antemoem burn is 
Select and explain. 
A. Heat rupture, B. Presence of soots beyond the tracheal bifurcation, C. Blackening of bones, D. Clean laryngeal airway
B: Presence of soots beyond the tracheal bifurcation
Answer: B: Presence of soots beyond the tracheal bifurcation 
Explanation: In case of burns, if death has occurred from suffocation,aspirated blackish coal paicles are seen in the nose,mouth,larynx,trachea,bronchi,oesophagus and stomach, and blood is cherry red. Presence of carbon paicles especially in the terminal bronchioles and an elevated CO saturation together are absolute proof that the victim was alive when the fire occurred. In the absence of CO in blood and soot in the airways,death may possibly result due to poisoning with carbon dioxide or deficiency of oxygen. Sometimes inhalation of smoke produces vomiting which may be inhaled and found in the smaller bronchi. Ref: K.S.Narayan Reddy's Synopsis of Forensic Medicine and Toxicology, 29th edition, Chapter 11, page-163.