The fluid in PCT is:

Correct Answer: B

Rationale: PCT fluid is isosmotic water follows Na reabsorption (e.g., ~65% reclaimed), matching plasma. Hyperosmotic requires concentration later nephron. Hypoosmotic needs dilution ascending limb. ADH affects distal not PCT. Isosmotic balance distinguishes it, key to proximal bulk flow, unlike osmotic shifts.

Correct Answer: C

Rationale: Respiratory isn't a chemical buffer physiological via COâ‚‚ excretion (e.g., lungs). Phosphate, bicarbonate, and proteins are chemical bind H directly. Respiratory's physiological role distinguishes it, key to system classification, unlike chemical buffers.

Correct Answer: B

Rationale: Kidneys, ureters, bladder, and urethra form the urinary system not liver/gallbladder (digestive), stomach/intestines (GI), or pancreas/spleen (endocrine/digestive). This lists core components, key for urine production/excretion, contrasting with non-urinary organs.

Correct Answer: A

Rationale: Aldosterone retains Na+ and excretes K+ not glucose (insulin), oxygen (lungs), or protein (liver). This specifies electrolyte control, critical for blood pressure, contrasting with unrelated functions.

Correct Answer: B

Rationale: Hematuria is blood in urine not glycosuria (glucose), proteinuria (protein), or anuria (no urine). This terms a key symptom, critical for injury/infection detection, contrasting with other conditions.