The most common, preventable complication of abdominal surgery is:

Correct Answer: A

Rationale: Atelectasis, the collapse of lung alveoli, is the most common preventable complication after abdominal surgery due to shallow breathing from pain or anesthesia effects. It's mitigated by deep breathing exercises and incentive spirometry. Fluid imbalance (B), thrombophlebitis (C), and urinary retention (D) occur but are less frequent and often less preventable with routine nursing interventions, making A the correct answer.

Correct Answer: D

Rationale: Inulin measures GFR (A) as it's filtered without tubular handling, its concentration rises in the proximal tubule (B) due to water reabsorption, and PAH measures RPF (C) as it's filtered and secreted, clearing most from plasma. All are true: inulin's properties suit GFR, its concentration reflects reabsorption, and PAH's clearance reflects RPF, making E (all are correct), reassigned as D, correct.

Correct Answer: D

Rationale: Angiotensin II (AII) increases sodium reabsorption (D) in the proximal tubule and via aldosterone, raising blood volume. It indirectly aids water (A), doesn't decrease sodium (B), and isn't self-forming (C), making D the key effect.

Correct Answer: C

Rationale: The collecting duct (C) becomes water-permeable with ADH via aquaporin-2, concentrating urine. The proximal tubule (A) and descending limb (B) are always permeable, and ascending limb (D) is not, making C the ADH-dependent match.

Correct Answer: A

Rationale: Inhibiting Na⁺ reabsorption in the PCT (A) reduces water reabsorption, increasing urine output (diuresis). Decreased output (B) contradicts this, and bilirubin (C) or fat (D) effects are unrelated to sodium, making A correct.