You are answering a USMLE-style medical question. Question: A 63-year-old woman comes to the physician because of a 6-month history of fatigue and shortness of breath on exertion in addition to a 1-month history of ankle swelling. She has a history of sleep apnea. Examination of the lower extremities shows bilateral pitting pedal and ankle edema. Cardiac examination shows a widely split S2 that varies with respiration. An ECG shows right bundle branch block. Which of the following is the most likely etiology of the patient's lower extremity edema? Options: A) Localized lymphatic obstruction B) Thrombus formation in a deep vein C) Increased capillary hydrostatic pressure D) Decreased plasma oncotic pressure " Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.