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
Diffusion of oxygen at the tissue level is affected in all the following poisoning except : 
Select and explain. 
A. Carbon monoxide, B. Curare, C. Phosgene, D. Cyanides
B: Curare
Answer: B: Curare 
Explanation: Curare is non-depolarizing (competitive) blocker, acts peripherally by causing muscle relaxation (and does not affect O2 diffusion).
Phosgene is an irritant gas causes lower respiratory tract damage.
Carbon monoxide and cyanide are chemical asphyxiants, i.e. prevent O2 from reaching tissue or the tissue from using it.