This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': "Ca prostate commonly metastasises to the vertebrae - \nSelect and explain. \nA. Because valveless communication exist with Batson' s periprostatic plexus., B. Via drainage to Sacral lymph node, C. Of direct Spread, D. None of above", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]