Which one of the following statements in regard to the excretion by the human kidneys is correct?

Options

A. Ascending limb of Loop of Henle is impermeable to electrolytes
B. Descending limb of Loop of Henle is impermeable to water
C. Distal convoluted tubule is incapable to reabsorbing `HCO_(3)^(-)`
D. Nearly 99 per cent of the glomerular filtrate is reabsorbed by the renal tubules

Answer

To solve the question regarding the correct statement about excretion by human kidneys, we will analyze each of the provided statements step by step.

### Step 1: Analyze the Statements
1. **Ascending limb of the loop of Henle is impermeable to electrolytes.**
- This statement is **incorrect**. The ascending limb of the loop of Henle is permeable to electrolytes (like sodium and chloride ions) but not to water.

2. **Descending limb of the loop of Henle is impermeable to water.**
- This statement is **incorrect**. The descending limb of the loop of Henle is actually permeable to water, allowing water to be reabsorbed into the surrounding medullary interstitium.

3. **DCT is incapable of reabsorbing HCO3.**
- This statement is **incorrect**. The distal convoluted tubule (DCT) can reabsorb bicarbonate (HCO3), which is important for maintaining acid-base balance in the body.

4. **Nearly 99% of the glomerular filtrate is reabsorbed by the renal tubules.**
- This statement is **correct**. About 180 liters of fluid is filtered daily, and approximately 99% of this filtrate is reabsorbed back into the bloodstream, with only about 1 to 1.5 liters excreted as urine.

### Step 2: Identify the Correct Statement
After analyzing all the statements, we find that the only correct statement is:
- **Nearly 99% of the glomerular filtrate is reabsorbed by the renal tubules.**

### Conclusion
The correct answer to the question is **Option D**.

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