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
In the absence of vasopressin, the greatest fraction of filtered water is absorbed in the 
Select and explain. 
A. Proximal tubule., B. Loop of Henle., C. Distal tubule., D. Cortical collecting duct.
A: Proximal tubule.
Answer: A: Proximal tubule. 
Explanation: Because the ratio of the concentration in tubular fluid to the concentration in plasma (TF/P) of the nonreabsorbable substance inulin is 2.5 to 3.3 at the end of the proximal tubule, it follows that 60–70% of the filtered solute and 60–70% of the filtered water have been removed by the time the filtrate reaches this point.