You are answering a USMLE-style medical question. Question: A 52-year-old man is brought to the emergency department with dry cough, shortness of breath, and low-grade fever that began 6 days ago. He also reports that he has had 3 episodes of watery diarrhea per day for the last 2 days. He appears slightly pale. His temperature is 38.0°C (100.4°F), pulse is 65/min, respirations are 15/min, and blood pressure is 140/78 mm Hg. Diffuse crackles are heard over bibasilar lung fields. Laboratory studies show: Hemoglobin 13.8 g/dL Leukocyte count 16,000/mm3 Platelet count 150,000/mm3 Serum Na+ 131 mEq/L Cl- 102 mEq/L K+ 4.7 mEq/L HCO3- 26 mEq/L Urea nitrogen 18 mg/dL Creatinine 1.2 mg/dL An x-ray of the chest shows patchy infiltrates in both lungs. Which of the following is the most appropriate pharmacotherapy?" Options: A) Levofloxacin B) Trimethoprim/sulfamethoxazole C) Amoxicillin D) Rifampin Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.