You are answering a USMLE-style medical question. Question: A 47-year-old woman is brought to the emergency department by paramedics. She was found unconscious on a park bench by a bystander. Her history is unobtainable. Vitals include a pulse of 64/min, a respiratory rate of 7/min, and a blood pressure of 110/70 mm Hg. On examination, the patient is unresponsive to voice and touch but shows a flexor response to pain. Her breathing is shallow. The pupils are constricted, and a response to light cannot be determined. An arterial blood gas sample reveals: pH 7.26 Pco2 70 mm Hg HCO3- 26 mEq/L Which of the following could explain this patient's presentation? Options: A) Diabetic ketoacidosis B) Diuretic overdose C) Hyperventilation D) Opioid overdose Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.