**Core Concept**
Glucose reabsorption in the kidneys is a critical process that maintains blood glucose levels within a narrow range. The kidneys reabsorb glucose back into the bloodstream from the filtrate in the early part of the proximal convoluted tubule (PCT). This process is facilitated by a specific transport mechanism that involves the sodium-glucose cotransporter 2 (SGLT2).

**Why the Correct Answer is Right**
The reabsorption of glucose in the early PCT occurs through a secondary active transport mechanism, where the sodium gradient generated by the Na+/K+-ATPase pump in the basolateral membrane drives the uptake of glucose into the renal tubular cells. The sodium-glucose cotransporter 2 (SGLT2) is a high-capacity, low-affinity transporter that mediates the reabsorption of glucose from the filtrate into the tubular cells. In the presence of high glucose levels, the SGLT2 transporter is upregulated to facilitate increased glucose reabsorption.

**Why Each Wrong Option is Incorrect**
**Option B:** The Henle loop is involved in the concentration and dilution of the urine, but it is not the primary site for glucose reabsorption. While the Henle loop does play a role in electrolyte and water balance, glucose reabsorption is not a significant function of this segment.
**Option C:** The collecting duct is primarily responsible for regulating the final concentration of the urine and is not involved in glucose reabsorption. The collecting duct's main function is to reabsorb water and electrolytes, not glucose.
**Option D:** The distal convoluted tubule is involved in the reabsorption of calcium and magnesium ions, but it is not the primary site for glucose reabsorption. The distal convoluted tubule does play a role in electrolyte balance, but glucose reabsorption is not a significant function of this segment.

**Clinical Pearl / High-Yield Fact**
The kidneys reabsorb approximately 99% of the filtered glucose load in the early PCT, with the remaining 1% being excreted in the urine. This process is critical for maintaining normoglycemia and preventing the loss of glucose in the urine.

✓ Correct Answer: A. Early PCT