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: Medicine
[{'content': 'Which parameter is almost same at apex and base of lung: March 2013 \nSelect and explain. \nA. pCO2, B. O2 concentration in blood, C. Ventilation, D. Perfusion', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B i.e. O2 concentration in blood At apex the O2 concentration is 20 ml/ 100 ml and at base the value is 19.2 ml/ 100 ml', 'role': 'assistant'}]