<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 21-year-old woman comes to the physician for the evaluation of dry cough and some chest tightness for the past several weeks. The cough is worse at night and while playing volleyball. She frequently has a runny nose and nasal congestion. Her mother has systemic lupus erythematosus. The patient has smoked one pack of cigarettes daily for the last 5 years. She does not drink alcohol. Her only medication is cetirizine. Her vital signs are within normal limits. Pulse oximetry on room air shows an oxygen saturation of 98. The remainder of the examination shows no abnormalities. Which of the following is the most appropriate next step in management?? A: Spirometry, B: Blood gas analysis, C: Methacholine challenge test, D: CT scan of the chest, E: Laboratory studies,  <response>: This is a clinical case scenario about a 21-year-old woman with dry cough, chest tightness, runny nose, and nasal congestion. The key findings are:- Dry cough and chest tightness, worse at night and during exercise, suggesting asthma- Runny nose and nasal congestion, suggesting allergic rhinitis- Smokes 1 pack per day for 5 years - Mother has SLE systemic lupus erythematosus- Vital signs normal, oxygen saturation 98 on room air- Physical exam unremarkableThe main differential diagnosis is asthma vs allergies. Additional testing is needed to confirm asthma and assess severity. Spirometry is the best next step to assess for reversible airway obstruction and bronchial hyperresponsiveness. Blood gas analysis and CT chest are not indicated based on the clinical presentation. Methacholine challenge can help confirm asthma but is more involved than simple spirometry. Lab studies are unlikely to be helpful diagnostically.A: Spirometry 