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: Pathology
[{'content': 'Common primary sites of metastasis to the brain are -a)  Thyroid Cab)  Tongue Cac)  Lung Cad)  Breast Cae)  Ovary Ca \nSelect and explain. \nA. acd, B. bcd, C. ad, D. b', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]