<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 65-year-old man comes to the physician for a follow-up examination. He has chronic obstructive pulmonary disease and was recently discharged from the hospital for an exacerbation. His cough and chills have since improved, but his mobility is still severely limited by dyspnea and fatigue. He smoked 2 packs of cigarettes daily for 30 years, but quit 5 years ago. His medications include inhaled daily budesonide, formoterol, and tiotropium bromide plus ipratropiumalbuterol as needed. Pulmonary function testing shows an FEV1 of 27 of predicted. Resting oxygen saturation ranges from 8488. Which of the following steps in management is most likely to increase the chance of survival in this patient?? A: Oral roflumilast, B: Oral theophylline, C: Antibiotic therapy, D: Oxygen therapy, E: Inhaled fluticasone,  <response>: This is a patient with severe COPD who has limited mobility due to dyspnea and fatigue. The key findings are the very low FEV1 indicating severe airflow obstruction and resting oxygen saturations of 84-88 indicating hypoxemia. The goal is to improve survival.Choice A roflumilast and Choice E inhaled fluticasone are incorrect because they are not proven to improve survival in COPD. Choice B theophylline can help dyspnea but has not been shown to improve survival.Choice C antibiotics may help treat an acute exacerbation but have not been shown to improve overall survival.Choice D oxygen therapy is the best answer. In COPD patients with resting hypoxemia, long-term oxygen therapy has been proven to increase survival.D: Oxygen therapy 