You are answering a USMLE-style medical question. Question: A 52-year-old man is brought to the emergency department because of worsening shortness of breath for 6 hours. For the past 5 days, he has had intermittent stabbing pain in the middle of his chest that worsens with lying down or taking deep breaths. He has also had a runny nose and a dry cough for the past 2 weeks. He has hypercholesterolemia and hypertension. He has smoked a pack of cigarettes daily for 34 years. His current medications include atorvastatin, enalapril, and hydrochlorothiazide. He appears pale and sweaty. His temperature is 38.3°C (100.9°F), pulse is 105/min, and respirations are 25/min. Blood pressure is 107/72 mm Hg during expiration and 86/65 mm Hg during inspiration. Examination shows jugular venous distention and pitting edema below the knees. Which of the following is the most likely cause of this patient's findings? Options: A) Dilation of the atria and ventricles B) Occlusion of a coronary artery C) Accumulation of fluid in the pericardial space D) Fibrous thickening of the pericardium Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.