Concept:The loop of Henle functions as a countercurrent multiplier, where the descending and ascending limbs have different permeabilities to water and electrolytes, essential for urine concentration.
Explanation:Statement (a) is correct: The descending limb is highly permeable to water but nearly impermeable to salts like Na⁺.
Statement (b) is correct: The loop of Henle creates a medullary osmotic gradient, which is crucial for concentrating urine (though final concentration occurs in the collecting duct).
Statement (c) is correct: Water is reabsorbed in the descending limb, and Na⁺ is actively reabsorbed in the thick ascending limb; thus both water and Na⁺ are reabsorbed in the loop.
Statement (d) is correct: The ascending limb uses both active transport (thick segment) and passive transport (thin segment) for electrolyte reabsorption.
Since all four statements (a), (b), (c), and (d) are true, but none of the given options include all four, no option is correct.
Answer:None of the given options are correct.
