<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:An 18-year-old boy presents to the clinic with shortness of breath and fever for the last 2 days. He also has a cough for the same duration. He is asthmatic and uses inhaled albuterol for symptom relief when required. He used albuterol today 3 times at 10-minute intervals but has not had relief of his symptoms. On physical examination, his temperature is 38.3C 101.0F, pulse is 130min, blood pressure is 11680 mm Hg, and respirations are 28min. Auscultation of the chest reveals bilateral crackles. Considering that he has already taken inhaled albuterol and has tachycardia, the physician nebulizes him with inhaled ipratropium bromide, which significantly improves his symptoms. Which of the following is the mechanism of action of this drug? ? A: Inhibition of degranulation of mast cells, B: Inhibition of phosphodiesterase-4, leading to prevention of release of cytokines and chemokines, C: Inhibition of adenosine receptors in the respiratory tract, D: Inhibition of vagally-mediated contraction of bronchial smooth muscles, E: Inhibition of vagally-mediated dryness in the respiratory mucosa,  <response>: This is a clinical vignette about an 18-year-old asthmatic boy who presents with shortness of breath, fever, and cough. He has used his albuterol inhaler without relief. On exam he has fever, tachycardia, tachypnea, and crackles. He is then given ipratropium bromide by nebulizer, which improves his symptoms. The question asks about the mechanism of action of ipratropium bromide. Based on the clinical scenario, this is likely an acute asthma exacerbation. Ipratropium bromide is an anticholinergic medication that blocks muscarinic receptors, leading to bronchodilation. Choice A is incorrect, as ipratropium does not affect mast cells or degranulation. Choice B is incorrect, as ipratropium does not inhibit phosphodiesterase-4. Choice C is incorrect, as ipratropium does not act on adenosine receptors. Choice D is correct, as ipratropium blocks muscarinic receptors on bronchial smooth muscle, preventing acetylcholine-mediated bronchoconstriction. This results in bronchodilation.Choice E is incorrect, as dry mucous membranes are mediated by acetylcholine on mucous glands, which ipratropium would inhibit, not cause.D: Inhibition of vagally-mediated contraction of bronchial smooth muscles 