**Core Concept**
Water reabsorption in the kidneys is a critical process for maintaining proper fluid balance and blood pressure. The renal tubules, particularly the proximal convoluted tubule (PCT), play a crucial role in water reabsorption. The process involves the movement of water from the filtrate into the surrounding interstitium, driven by osmotic forces and facilitated by specific transport mechanisms.

**Why the Correct Answer is Right**
Water reabsorption is most efficient in the PCT, where approximately 65-70% of filtered water is reabsorbed. This occurs due to the high osmotic gradient created by the reabsorption of glucose, sodium, and other solutes. Water reabsorption is facilitated by aquaporin-1 (AQP1) water channels, which are expressed in the apical membrane of PCT cells. The movement of water from the filtrate into the interstitium is driven by the osmotic gradient, allowing for efficient reabsorption of water back into the bloodstream.

**Why Each Wrong Option is Incorrect**
**Option A:** The descending limb of the loop of Henle is involved in water reabsorption, but it is not the primary site of maximal water reabsorption.
**Option B:** The collecting duct is responsible for fine-tuning water reabsorption, but it is not the site of maximal water reabsorption.
**Option C:** The distal convoluted tubule (DCT) is involved in electrolyte reabsorption, but it is not the primary site of maximal water reabsorption.

**Clinical Pearl / High-Yield Fact**
The PCT is responsible for reabsorbing approximately 65-70% of filtered water, with the remaining water being reabsorbed in the collecting duct under the influence of antidiuretic hormone (ADH). This highlights the importance of the PCT in water reabsorption and the role of ADH in regulating water balance.

**Correct Answer:** C. Proximal convoluted tubule