This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General surgery, Subject name: Surgery
[{'content': 'Most common cause of brain metastases \nSelect and explain. \nA. Lung, B. Liver, C. Breast, D. Melanoma', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Origin PercentageLung 40Breast 15Melanoma 10Renal/genitourinary 10Other/unknown 25Ref: Bailey and love 27e pg: 664', 'role': 'assistant'}]