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: Radiology
[{'content': 'Percentage of cold thyroid nodules likely to be malignant: \nSelect and explain. \nA. 20%, B. 30%, C. 40%, D. 72%', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. 20%', 'role': 'assistant'}]