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': 'The first investigation of choice in a patient with suspected subarachnoid haemorrhage should be - \nSelect and explain. \nA. Non-contrast computed tomography, B. CSF examination, C. Magnetic resonance imaging (MRI), D. Contrast-enhanced computed tomography', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Investigation of choice for acute SAH is non-contrast CT scan.', 'role': 'assistant'}]