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 oliguria - 
Select and explain. 
A. Excretion of less than 300 ml in 24 hrs, B. Excretion of less than 500 ml in 24 hrs, C. Excretion of less than 300 ml in 12 hrs, D. Excretion of less than 100 ml in 24 hrs
B: Excretion of less than 500 ml in 24 hrs
Answer: B: Excretion of less than 500 ml in 24 hrs 
Explanation: None