This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Trauma, Subject name: Surgery
Cerebral perfusion pressure is 
Select and explain. 
A. mean aerial pressure + intracranial pressure, B. cerebral blood flow * brain surface area in m^2, C. cerebral blood flow / brain surface area in m^2, D. mean aerial pressure - intracranial pressure
D: mean aerial pressure - intracranial pressure
Answer: D: mean aerial pressure - intracranial pressure 
Explanation: Cerebral perfusion pressure (CPP), is the difference between mean aerial pressure (MAP) and intracranial pressure (ICP): CPP (75-105 mmHg) = MAP (90-110 mmHg) - ICP (5-15 mmHg).Normal cerebral blood flow (CBF) is about 55 mL/minute for every 100 g of brain tissue. Ischaemia results when this rate drops below 20 mL/min,Bailey and love 26e pg: 310