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': 'In case of subarachnoid haemorrhage, investigation of choice is: March 2011 \nSelect and explain. \nA. Non contrast CT scan, B. MRI, C. MRI angio with imaging, D. Ultrasound', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A: Non contrast CT scan The diagnosis of SAH can be made on CT, but a negative result does not exclude the diagnosis since small amounts of blood in the subarachnoid space cannot be detected by CT', 'role': 'assistant'}]