The main function of Henle’s loop is to conserve water. It does this by creating a concentration gradient in the medulla of the kidney. The descending limb of the loop is permeable to water, but the ascending limb is not. This allows water to flow out of the loop into the medulla, while salt is retained. The result is a concentrated medullary interstitium. This concentration gradient is then used to reabsorb water from the collecting duct, which helps to concentrate the urine.
Option A is incorrect because the passage of urine is the function of the ureters. Option B is incorrect because the filtration of blood is the function of the glomerulus. Option C is incorrect because the formation of urine is a complex process that involves multiple parts of the nephron, including the glomerulus, proximal tubule, distal tubule, and collecting duct.