To solve this problem, we need to analyze the permeability characteristics of the loop of Henle in the nephron. Let's evaluate each statement:$\newline \bullet$Option 1: The descending limb of loop of Henle is impermeable to water.$\newline$ - This statement is incorrect. The descending limb of the loop of Henle is permeable to water but impermeable to electrolytes.$\newline \bullet$Option 2: The ascending limb of loop of Henle is permeable to water.$\newline$ - This statement is incorrect. The ascending limb of the loop of Henle is impermeable to water but permeable to electrolytes.$\newline \bullet$Option 3: The descending limb of loop of Henle is permeable to electrolytes.$\newline$ - This statement is incorrect. The descending limb is permeable to water, not electrolytes.$\newline \bullet$Option 4: The ascending limb of loop of Henle is impermeable to water.$\newline$ - This statement is correct. The ascending limb is indeed impermeable to water and allows the reabsorption of electrolytes.$\newline$Therefore, the correct statement is Option 4: The ascending limb of loop of Henle is impermeable to water.