When the oxygen content of the blood decreases, the kidneys will release

Correct Answer: A

Rationale: Low blood oxygen triggers erythropoietin release stimulates RBC production (e.g., peritubular cells). Renin responds to pressure not oxygen. Angiotensin is RAAS product not kidney-released. Calcitriol is vitamin D not oxygen-linked. Erythropoietin's hypoxia response distinguishes it, key to oxygenation, unlike pressure or mineral roles.

Correct Answer: D

Rationale: Tubular reabsorption primarily occurs in the PCT ~65-70% of filtrate (e.g., Na , water, glucose). Collecting duct adjusts less volume. Distal tubule fine-tunes smaller role. Capsule filters not reabsorbs. PCT's dominance distinguishes it, critical for bulk reclamation, unlike later or filtration sites.

Correct Answer: A

Rationale: PCT (~65% water) and collecting duct (ADH-driven) increase water reabsorption e.g., bulk and regulated recovery. Distal tubule adjusts less water focus. Loop sets gradient not ADH-dependent. PCT/collecting synergy distinguishes it, key to water conservation, unlike partial or gradient-focused pairs.

Correct Answer: C

Rationale: The JGA is between afferent arteriole and distal tubule macula densa/JG cells (e.g., renin release site). Loop is tubular not vascular. Medulla oblongata is brain unrelated. Collecting/PCT lacks JGA wrong. JGA's position distinguishes it, critical for GFR/BP control, unlike tubular or brain errors.

Correct Answer: B

Rationale: Urine is ~95% water rest solutes (e.g., urea, ions ~5%). 100% ignores solutes false. 90% underestimates water too low. 85% overestimates solutes incorrect. 95% distinguishes it, critical for urine composition, unlike absolute or skewed estimates.