You are answering a USMLE-style medical question. Question: A 43-year-old woman is brought to the emergency department by her brother for severe chest pain. The patient recently lost her husband in a car accident and is still extremely shocked by the event. On physical examination, her blood pressure is 105/67 mm Hg, the heart rate is 96/min and regular, breathing rate is 23/min, and the pulse oximetry is 96%. An S3 heart sound and rales in the lower right and left lung lobes are heard. A 12-lead ECG shows no significant findings. Echocardiography shows an enlarged left ventricle and left atrium. The patient is stabilized and informed about the diagnosis and possible treatment options. Which of the following is the most likely diagnosis? Options: A) Atrial fibrillation B) Constrictive pericarditis C) Takotsubo cardiomyopathy D) Restrictive cardiomyopathy Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.