This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Medicine
Oliguria is defined as - 
Select and explain. 
A. 24 hour urine output <200 ml, B. 24 hour urine output <300 ml, C. 24 hour urine output <400 ml, D. 24 hour urine output <500 ml
C: 24 hour urine output <400 ml
Answer: C: 24 hour urine output <400 ml 
Explanation: Ans. is 'c' i.e., 24 hour urine output <400 ml Oliguria and Anuria* Oliguria refers to a 24-h urine output <400 mL, and* Anuria is the complete absence of urine formation (<100 mL in 24 hours).