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

Options

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

Answer

To determine the correct statement regarding excretion by the human kidneys, let's analyze each of the provided options step by step.

### Step 1: Analyze the first option
**Statement:** "Distal convoluted tubule is incapable of reabsorbing HCO3 ion."
- The distal convoluted tubule (DCT) does have the ability to reabsorb bicarbonate (HCO3-), although it is not the primary site for this process. Therefore, this statement is incorrect.

### Step 2: Analyze the second option
**Statement:** "Nearly 99% of glomerular filtrate is reabsorbed by the renal tubules."
- It is known that approximately 180 liters of fluid is filtered from the blood daily by the nephrons, and about 99% of this filtrate is reabsorbed back into the bloodstream. This means that only about 1 to 1.5 liters is excreted as urine. This statement is correct.

### Step 3: Analyze the third option
**Statement:** "Ascending limb of loop Henle is impermeable to electrolytes."
- The ascending limb of the loop of Henle is indeed impermeable to water but is permeable to electrolytes, specifically sodium and chloride ions. Therefore, this statement is incorrect.

### Step 4: Analyze the fourth option
**Statement:** "Descending limb of loop of Henle is impermeable to water."
- The descending limb of the loop of Henle is actually permeable to water, allowing for water reabsorption. Therefore, this statement is also incorrect.

### Conclusion
After analyzing all the options, the correct statement regarding excretion by the human kidneys is:
**"Nearly 99% of glomerular filtrate is reabsorbed by the renal tubules."** (Option B)

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