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
Primary investigation of choice in a patient with suspected subarachnoid haemorrhage should be: 
Select and explain. 
A. Non-contrast computed tomography, B. Magnetic resonance imaging (MRI), C. Contrast-enhanced computed tomography, D. Lumbar punture
A: Non-contrast computed tomography
Answer: A: Non-contrast computed tomography 
Explanation: 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