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': 'Which of the following signs suggest benign nature in the evaluation of solitary pulmonary nodule on CT scan? \nSelect and explain. \nA. Air bronchogram in nodule, B. Presence of amorphous calcification, C. Fat density within the lesion, D. Spiculated outline', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Fat density within the lesion is characteristic of hamartoma.', 'role': 'assistant'}]