This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Blood, Subject name: Medicine
[{'content': 'Which of the following typically causes a macrocytic anemia? \nSelect and explain. \nA. blind loop syndrome, B. iron deficiency, C. thalassemia, D. chronic inflammation', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Blind loop syndrome leads to megaloblastic anemia and macrocytosis because of B12 deficiency. The deficiency is caused by colonization with bacteria that takes up ingested cobalamin before it can be absorbed. The other conditions generally cause microcytic or normocytic anemias.', 'role': 'assistant'}]