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': 'Primary investigation of choice in a patient with suspected subarachnoid haemorrhage should be: \nSelect and explain. \nA. Non-contrast computed tomography, B. Magnetic resonance imaging (MRI), C. Contrast-enhanced computed tomography, D. Lumbar punture', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Here the investigation of choice is Non-contrast CT; if it is not successful lumbar puncture can be tried. The most sensitive investigation is Digital subtractions angiography of both carotid and veebral aeries. Ref: Mauricio Castillo (2006), Chapter 8, "Trauma", In the Book, "Neuroradiology Companion: Methods, Guidelines, and Imaging Fundamentals" 3rd Edition, Lippincotts Publications, USA, Page 52 ; Current Medical Diagnosis and Treatment, 2003, Page 965', 'role': 'assistant'}]