Which of the following statements about the reabsorption process in Henle's loop are correct? (a) The descending limb is permeable to water but almost impermeable to electrolytes; (b) Urine gets concentrated in Henle's loop; (c) Reabsorption of Na⁺ and water takes place in Henle's loop; (d) Active or passive transport of electrolytes occurs in the ascending limb.

Solution & Explanation

Statement (a) is correct (descending limb: permeable to water, nearly impermeable to electrolytes). However, the loop of Henle has minimal direct reabsorption of substances — its main role is to set up the medullary concentration gradient (counter-current); the urine is finally concentrated chiefly in the collecting duct, and the ascending limb is impermeable to water while transporting electrolytes out. Because no single option correctly combines only the true statements, the question was marked as having no fully correct option.