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: Medicine
[{'content': 'For cystic lesions in brain, investigation of choice is: \nSelect and explain. \nA. Ultrasound, B. Angiography, C. C.T. Scan, D. MRI scan', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]