This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment & Nutritional Pathology, Subject name: Pathology
[{'content': "A 47-year-old man presents with a 6-week history of increasing fatigue and dark-colored stools. Complete blood count shows hemoglobin of 8.6 g/dL and microcytic, hypochromic RBCs. Upper gastrointestinal endoscopy reveals a peptic ulcer along the lesser curvature of the stomach. This patient's anemia is most likely caused by deficiency of which of the following? \nSelect and explain. \nA. Folic acid, B. Iron, C. Thiamine, D. Vitamin B12", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Gastrointestinal hemorrhage leads to the loss of heme iron at a rate faster than it is replaced from dietary sources. The result is microcytic hypochromic anemia. The anemias associated with deficiencies of folic acid (choice A) and vitamin B12 (choice D) are macrocytic.Diagnosis: Iron-deficiency anemia', 'role': 'assistant'}]