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
What is the best guide for the management of fluid resuscitation? 
Select and explain. 
A. CVP, B. Blood pressure, C. Oxygen saturation, D. Urine output
D: Urine output
Answer: D: Urine output 
Explanation: None