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: Pediatrics
[{'content': 'Which of the following is a feature of Acute severe asthma \nSelect and explain. \nA. Heart rate of 110 beats / min, B. Pa O2 of 70 mmHg, C. Peak expiratory flow rate of < 40 %, D. All of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Features of Acute Severe Asthma\n\nHeart rate > 120 beats / min\nPa O2 of < 60 mmHg\nPeak expiratory flow rate of < 40 %', 'role': 'assistant'}]