Final answer:
The ascending limb of the loop of Henle is impermeable to water and reabsorbs Na, K, and Cl.
Step-by-step explanation:
The site in the nephron that is impermeable to water and reabsorbs Na, K, and Cl is the ascending limb of the loop of Henle. The ascending limb is lined with simple cuboidal epithelium without aquaporin proteins, which makes it completely impermeable to water. However, it actively reabsorbs ions like Na, K, and Cl through cotransport systems. This reabsorption of ions contributes to the hyperosmotic environment in the kidney medulla.