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: Medicine
Which of the following correlates well with the "severe" type of bronchial asthma exacerbation: March 2011 
Select and explain. 
A. Bradycardia with HR less than 100/ min, B. Pulsus paradoxus less than 10/min, C. Tachypnea with RR less than 30/min, D. Usual use of accessory muscles of respiration
D: Usual use of accessory muscles of respiration
Answer: D: Usual use of accessory muscles of respiration 
Explanation: Ans. D: Usual use of accessory muscles of respiration Bronchial asthma: Hyper-responsiveness of airways with bronchoconstriction Increased leukotrienes Histology: Creola bodies, - Charcot Layden crystals, - Curschmann's spiral FEV1 is the parameter to improve maximum on bronchodilator therapy