This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Physiology
[{'content': 'Pleural pressure positive in \nSelect and explain. \nA. End of inspiration, B. End of expiration, C. End of forced expiration, D. Sta or beginning of inspiration', 'role': 'user'}, {'content': 'Answer: C \nExplanation: During active expiration, the abdominal muscles are contracted to force up the diaphragm and the resulting pleural pressure can become positive. Positive pleural pressure may temporarily collapse the bronchi and cause limitation of air flow Ref: guyton and hall textbook of medical physiology 12 edition page number:316,317,318', 'role': 'assistant'}]