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: Physiology
[{'content': 'Aerial blood gas analysis in Carbon monoxide poisoning shows: \nSelect and explain. \nA. PO2 less, O2 saturation normal, B. PO2 normal, O2 saturation less with normal or slightly decreased PCO2, C. PO2 less, O2 saturation normal, D. PO2 less, O2 saturation decreased', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. PO2 normal O2, saturation less with normal or slightly decreases PCO2.', 'role': 'assistant'}]