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': 'All are true about thymus swelling except – \nSelect and explain. \nA. Widening of mediastinum on X–ray, B. Sharp border with sail like appearance, C. Steroid administration reduces size of swelling, D. Shift of trachea on X–ray', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Thymic shadow does not indent tracheal shadow. A mediastinal shadow indenting tracheal shadow should always be evaluated for a significant pathology.\nThymic swelling may cause widening of anterior mediastinum. Thymic swelling causes a sail-shaped shadow. Thymic swelling may shrink with use of steroids.', 'role': 'assistant'}]