This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
[{'content': 'During 3rd month of gestation, hematopoiesis occurs in \nSelect and explain. \nA. Liver, B. Thymus, C. Spleen, D. Bone marrow', 'role': 'user'}, {'content': 'Answer: A \nExplanation: From 3rd month of gestation liver and spleen become main site of hematopoiesis-Hepatic phaseSpleen makes smaller contribution compared to liverRef: Medical Physiology Indu Khurana 2015 edition page No:104', 'role': 'assistant'}]