You are answering a USMLE-style medical question. Question: A 56-year-old man comes to the emergency department because of nausea and shortness of breath that started while he was at work one hour ago. He also reports lightheadedness that started earlier in the day. He has type 2 diabetes mellitus, for which he takes metformin and sitagliptin. He has smoked 1 pack of cigarettes daily for 20 years. He appears pale and diaphoretic. A 12-lead ECG is shown. Which of the following is the most likely underlying cause of this patient's symptoms? Options: A) Viral myocarditis B) Acute pericarditis C) Acute inferior myocardial infarction D) Saddle pulmonary embolus Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.