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: Unknown
[{'content': 'A metastatic carcinoma in the brain of an adult most often comes from a primary in the - \nSelect and explain. \nA. Stomach, B. Ovary, C. Oral cavity, D. Lung', 'role': 'user'}, {'content': 'Answer: D \nExplanation: answer: D', 'role': 'assistant'}]