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: Medicine
Blood flow in hemodialysis machine 
Select and explain. 
A. 100-200 ml/min, B. 300-500 ml/min, C. 700-800 ml/min, D. >1000 ml/min
B: 300-500 ml/min
Answer: B: 300-500 ml/min 
Explanation: Blood flow - 300-500 ml/min.
Dialysate - 500-800 ml/min in opposite direction.