Normal urine excludes glucose in healthy individuals

Steps:

• Recall that urine forms from blood filtration in kidneys, reabsorbing essentials like water, salts, and nutrients.
• Identify key urine components: water as solvent, urea from protein breakdown, salts for electrolyte balance.
• Note glucose is fully reabsorbed in proximal tubules under normal conditions.
• Compare options to standard urine composition to find the absent substance.

Why A is correct:

• Kidneys reabsorb 100% of filtered glucose via active transport in healthy individuals, preventing its excretion (per renal physiology).

Why the others are wrong:

• B: Salts (e.g., sodium, potassium) are excreted to maintain osmotic balance.
• C: Urea is a primary nitrogenous waste product routinely eliminated in urine.
• D: Water comprises 95% of urine volume for waste dilution and excretion.

Final answer: A