You are answering a USMLE-style medical question. Question: A 56-year-old man is brought to the emergency department. He was found unconscious on the street. The staff recognizes him as a local homeless man with a long history of alcoholism. At the hospital, his pulse is 95/min, the blood pressure is 110/70 mm Hg, the respirations are 20/min, and the oxygen saturation is 98% on room air. On physical exam, the unconscious man is covered in bloody vomit with small clots and food particles. He smells of alcohol. A digital exam reveals black tarry stool in the rectal vault. The patient is given oxygen, IV fluids, and an NG-tube is placed and set to intermittent suction. Labs are sent and the patient is prepared for a procedure. Which of the following is the most appropriate next step in his management? Options: A) Undergo colonoscopy B) Undergo upper GI endoscopy C) Proton pump inhibitors with anti-H.pylori regimen D) Surgery for peptic ulcer disease Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.