You are answering a USMLE-style medical question. Question: Three days after undergoing an open cholecystectomy, an obese 57-year-old woman has fever, chills, and a headache. She has right-sided chest pain that increases on inspiration and has had a productive cough for the last 12 hours. She had an episode of hypotension after the operation that resolved with intravenous fluid therapy. She underwent an abdominal hysterectomy 16 years ago for multiple fibroids of the uterus. She has smoked one pack of cigarettes daily for 17 years. She appears uncomfortable. Her temperature is 39°C (102.2°F), pulse is 98/min, respirations are 18/min, and blood pressure is 128/82 mm Hg. Inspiratory crackles are heard at the right lung base. The abdomen is soft and nontender. There is a healing surgical incision below the right ribcage. The remainder of the examination shows no abnormalities. Which of the following is the most likely diagnosis? Options: A) Pulmonary embolism B) Subphrenic abscess C) Pneumonia D) Pneumothorax Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.