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
Concerning normal expiration during resting conditions: 
Select and explain. 
A. Expiration is generated by the expiratory muscles, B. Alveolar pressure is less than atmospheric pressure, C. Intrapleural pressure gradually falls (becomes more negative) during the expiration, D. Flow velocity of the gas (in cm/sec) in the large airways exceeds that in the terminal bronchioles
D: Flow velocity of the gas (in cm/sec) in the large airways exceeds that in the terminal bronchioles
Answer: D: Flow velocity of the gas (in cm/sec) in the large airways exceeds that in the terminal bronchioles 
Explanation: The velocity of the gas in the large airways exceeds that in the terminal bronchioles because the latter have a very large combined cross-sectional area. The other choices are incorrect: Under resting conditions, expiration is passive it is associated with an alveolar pressure that exceeds atmospheric pressure intrapleural pressure gradually increases (becomes less negative) during expiration and the diaphragm moves up as expiration proceeds.