You are answering a USMLE-style medical question. Question: A 60-year-old man presents with a 2-day history of increasing difficulty in breathing with a productive cough. He reports having shortness of breath over the last 6 months, but he has felt worse since he contracted a cold that has been traveling around his office. Today, he reports body aches, headache, and fever along with this chronic cough. His past medical history is significant for prediabetes, which he controls with exercise and diet. He has a 30-pack-year smoking history. His blood pressure is 130/85 mmHg, pulse rate is 90/min, temperature is 36.9°C (98.5°F), and respiratory rate is 18/min. Physical examination reveals diminished breath sounds bilateral, a barrel-shaped chest, and measured breathing through pursed lips. A chest X-ray reveals a flattened diaphragm and no signs of consolidation. Pulmonary function testing reveals FEV1/FVC ratio of 60%. Arterial blood gases (ABG) of this patient are most likely to reveal which of the following? Options: A) Primary respiratory acidosis B) Primary respiratory alkalosis C) Compensatory respiratory acidosis D) Anion gap metabolic acidosis with respiratory alkalosis Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.