You are answering a USMLE-style medical question. Question: A 65-year-old male presents to the emergency department from his home complaining of dyspnea. He is alert and oriented. The following arterial blood gas readings are drawn: pH: 7.33 (Normal: 7.35-7.45), pCO2: 70 mmHg (Normal: 35-45 mmHg), HCO3 33 (Normal: 21-26 mEq/L) Which of the following is most likely to have produced this patient’s condition? Options: A) Panic attack B) Mechanical ventilation C) Pulmonary embolus D) Chronic obstructive bronchitis Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.