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': 'Most of the airway resistance is from: \nSelect and explain. \nA. Terminal bronchioles, B. Respiratory bronchioles, C. Medium sized bronchi, D. Trachea', 'role': 'user'}, {'content': 'Answer: D \nExplanation: 23 generations of respiratory tree:\n\nTrachea – 0th generation\nFurther divisions – new generations\xa0\nFirst 7 generations\xa0\n\t\nCartilaginous\nNon cartilaginous\n\n\nLast 16 generations\xa0\n\t\nNon cartilaginous\nCompressible\nThin layer of smooth muscles +nt\nSome neuro endocrine cells +nt\n\n\nAPUD\nKULCHITSKY CELLS\n\nFirst 16 generations - Conducting zone (dead space)\nLast 7 Non cartilaginous – Respiratory zone\nNote:\nOut of first 16 generations, trachea ( 0th generation ) offers maximum resistance.\nReference: GUYTON AND HALL TEXTBOOK OF MEDICAL PHYSIOLOGY, THIRTEENTH EDITION(INTERNATIONAL EDITION)', 'role': 'assistant'}]