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: Physiology
Which of the following causes maximal cerebral vasodilation: 
Select and explain. 
A. Hypercarbia, B. Hypoxia, C. Lactic Acidosis, D. Exercise
A: Hypercarbia
Answer: A: Hypercarbia 
Explanation: A i.e. Hypercarbia