<prompt> True regarding water absorption in tubules:September 2007Majority of facultative reabsorption occurs in proximal tubuleBulk of water reabsorption occurs secondary to sodium absorption25 of water is reabsorbed irrespective of water balanceObligatory reabsorption is ADH dependent  <response>: Ans. B: Bulk of water reabsorption occurs secondary to sodium absorptionWater reabsorption keeps pace with the sodium reabsorption in the proximal tubules and hence the concentration of sodium and total osmolarity remains the same. 