A patient with chronic kidney disease develops hyperkalemia. Which of the following drugs is most likely to exacerbate this condition by inhibiting the secretion of potassium in the collecting duct?

✓ Correct Answer: Option C

Spironolactone is a potassium-sparing diuretic that acts as an aldosterone antagonist. It blocks aldosterone's effects in the collecting duct, leading to decreased sodium reabsorption and, crucially, decreased potassium and hydrogen ion secretion, thereby increasing serum potassium.