Water is returned to the blood from the proximal convoluted tubule by

Correct Answer: B

Rationale: Water returns from PCT by osmosis follows Na gradient (e.g., isosmotic reabsorption). Active transport moves Na not water directly. Facilitated diffusion is glucose not water. Carrier molecules aid solutes not primary water. Osmosis's passive flow distinguishes it, critical for PCT water recovery, unlike active or facilitated mechanisms.

Correct Answer: A

Rationale: The JGA monitors blood volume senses pressure via JG cells (e.g., renin adjusts). Medulla oblongata controls breathing not volume. Midbrain is motor unrelated. Hypothalamus senses osmolarity not volume directly. JGA's volume role distinguishes it, key to RAAS, unlike neural or osmotic structures.

Correct Answer: A

Rationale: Pyelonephritis is kidney infection e.g., bacterial ascent (pelvis/nephrons). Cystitis is bladder not kidney. Urethritis is urethra lower. Hypertension is BP not infection. Pyelonephritis's site distinguishes it, key to renal pathology, unlike lower tract or unrelated conditions.

Correct Answer: B

Rationale: Alcohol is the key diuretic inhibiting ADH suppresses pituitary release (e.g., increases urine output). Water dilutes plasma stimulates ADH. Vitamin B₁₂ is metabolic not diuretic. Na influences reabsorption not ADH directly. Alcohol's ADH block distinguishes it, critical for diuresis, unlike dilution or unrelated factors.

Correct Answer: C

Rationale: Proximal convoluted tubule (PCT) cells have the most mitochondria e.g., fuel Na /K ATPase for 65% reabsorption. Skeletal muscle has many less than PCT. Liver is metabolic not reabsorptive. Cardiac muscle sustains beating less dense. PCT's energy demand distinguishes it, key to reabsorption, unlike muscle or liver cells.