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
Which of the following is the best parameter to assess fluid intake in a poly-trauma patient? 
Select and explain. 
A. Urine output, B. BP, C. Pulse, D. Pulse oximetry
A: Urine output
Answer: A: Urine output 
Explanation: None