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: Surgery
A young man is brought to the emergency depament with head injury following a motor vehicle accident. The patient is unconscious. BEST prognostic factor for head injury is: 
Select and explain. 
A. Glasgow coma scale, B. Age, C. Mode of injury, D. CT findings
A: Glasgow coma scale
Answer: A: Glasgow coma scale 
Explanation: In severe head injury, the clinical features of eye opening, motor responses of the limbs, and verbal output have been found to be generally predictive of outcome. These three responses are assessed by the Glasgow Coma Scale; a score between 3 and 15 is assigned. Over 85% of patients with aggregate scores of Ref: Ropper A.H. (2012). Chapter 378. Concussion and Other Head Injuries. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.