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: Physiology
What is the net urea reabsorption rate? 
Select and explain. 
A. 0 mg/min, B. 25 mg/min, C. 50 mg/min, D. 75 mg/min
D: 75 mg/min
Answer: D: 75 mg/min 
Explanation: The net urea reabsorption rate is equal to the ﬁltered load of urea (GFR  x plasma urea concentration ) - urinary excretion rate of urea (urine urea concentration  x  urine ﬂow rate ). ​
Therefore, net urea reabsorption = (50 mL/min x 2.5 mg/mL) – (50 mg/mL x 1 mL/min) = 75 mg/min.