Which ion is reabsorbed in exchange for sodium?

Correct Answer: B

Rationale: Potassium is reabsorbed in exchange for sodium in the distal tubule (Na+/K+ pump), not chloride (co-transported), calcium, or magnesium (different mechanisms). This distinguishes ion exchange, key for electrolyte balance, contrasting with passive processes.

Correct Answer: B

Rationale: Minor calyces collect urine from papillae first, before pelvis, ureter, or urethra. This identifies initial collection, key for urine flow, contrasting with downstream structures.

Correct Answer: A

Rationale: Creatine isn't secreted (converted to creatinine), unlike creatinine, H+ (acid-base), and penicillin (drugs). This distinguishes secretion profile, key for excretion, contrasting with metabolized compounds.

Correct Answer: B

Rationale: Micturition reflex integrates in the sacral spinal cord (S2-S4), not medulla (respiration), hypothalamus (hormones), or lumbar (lower). This locates reflex center, key for bladder control, contrasting with higher regions.

Correct Answer: A

Rationale: Countercurrent multiplier increases NaCl in the medullary interstitium, not decreases, or affects potassium. This defines concentration gradient, key for water reabsorption, contrasting with potassium roles.