You are answering a USMLE-style medical question. Question: A 55-year-old man is brought to the emergency room by his wife for severe abdominal pain for the past 1 hour. He is unable to give more information about the nature of his pain. His wife says that he has peptic ulcer disease and is being treated with antacids without a good response. She adds that he vomited repeatedly in the last couple of hours, his vomitus being brown/red in color. His temperature is 98.6°F (37°C), respiratory rate is 16/min, pulse is 97/min, and blood pressure is 100/68 mm Hg. A physical exam reveals a tense abdomen with a board like rigidity and positive rebound tenderness. An erect abdominal x-ray is ordered. Which of the following is the most likely diagnosis? Options: A) Duodenal peptic ulcer B) Gastric peptic ulcer C) Pancreatitis D) Perforated gastric peptic ulcer Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.