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
[{'content': 'Which one of the following statements regarding water reabsorption in the tubules is true? \nSelect and explain. \nA. The bulk of water reabsorption occurs secondary to Na+ reabsorption, B. Majority of facultative reabsorption occurs in proximal tubule, C. Obligatory reabsorption is ADH dependent, D. 20% of water is always reabsorbed irrespective of water balance', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Maximum of filtered water (60-70%) is reabsorbed in the proximal tubule, with or without Vasopressin. This is independent of the fluid and electrolyte status of the body and is caused by the osmotic gradient created by Na+ reabsorption.\nObligatory water reabsorption- (Independent of ADH)- 85%\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Proximal tubule- 60-70%\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Descending limb of loop of Henle- 15%\nFacultative water reabsorption- (ADH dependent)- 15%\nThis depends on fluid and electrolyte status of the body\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Late distal tubule\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Cortical collecting duct\nMedullary collecting duct', 'role': 'assistant'}]