A 56-year-old woman presents to the hospital because of symptoms of dyspnea, blurry vision, and headaches. The symptoms started that morning and are getting worse. Her past medical history is significant for hypertension and osteoarthritis. She stopped taking her anti-hypertensive medications 3 months ago because of side effects.On examination, her blood pressure is 210/130 mm Hg, heart rate 100 beats/min, and oxygen saturation 95%. Her fundi reveal retinal hemorrhages and papilledema. The heart sounds are normal expect for an S4, and the lungs have lower lobe crackles. Which of the following is the most appropriate agent to reduce her blood pressure?