You are answering a USMLE-style medical question. Question: A 65-year-old woman is brought to the emergency department by her husband after he found her with nausea, headache, and agitation 1 hour ago. When he left their lakeside cabin 6 hours before to go ice fishing and get more firewood, she did not have any symptoms. She has chronic migraines, hypertension, and type 2 diabetes mellitus. Her medications include lisinopril and metformin, but she ran out of her anti-hypertensive medications over the weekend. Her temperature is 37.1°C (98.8°F), pulse is 110/min, respirations are 21/min, and blood pressure is 154/92 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 98%. She is confused and oriented only to person and place. She recalls only one of three objects after 5 minutes. Her gait is unsteady. Physical examination shows no abnormalities. Which of the following is the most effective intervention for this patient's current condition? Options: A) Intravenous nitroprusside B) Hyperbaric oxygen therapy C) 100% oxygen therapy D) Heliox therapy Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.