This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System Pa 1, Subject name: Physiology
[{'content': 'Percentage of Normal dead space is:- \nSelect and explain. \nA. 50-70, B. 20-Oct, C. 30-40, D. 80-90', 'role': 'user'}, {'content': "Answer: C \nExplanation: Dead space - Some of the air a person breathes never reaches the gas exchange areas but simply fills respiratory passages where gas exchange does not occur, such as the nose, pharynx & trachea. - The air is called 'dead space air' because its not useful for gas exchange. - Normal tidal volume = 500 m - Normal dead space = 150 m Thus, Normal dead space ratio = 30 - 40%", 'role': 'assistant'}]