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': 'Best test to determine etiology of SAH – \nSelect and explain. \nA. Enhanced CT, B. Unenhanced CT, C. Intra arterial digital substraction angiography, D. MRI', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Investigation of choice to know the etiology of SAH is four vessels digital substraction angiography.', 'role': 'assistant'}]