This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thorax, Subject name: Anatomy
[{'content': 'Lymphatic drainage of the outer upper quadrant of the breast is mainly to: \nSelect and explain. \nA. Anterior axillary group, B. Internal mammary group, C. Posterior axillary group, D. Apical nodes', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans: a (Anterior axillary nodes) Ref: BDC Vol. I, 4th ed, p. 42About 75% of the lymphatics from the breast drain into the axillary nodes. Among the axillary nodes, the lymphatics mostly end in the anterior group (pectoral group), closely related to the axillary tail of the breast.', 'role': 'assistant'}]