A nurse is caring for a client who is taking digoxin to treat heart failure. Which of the following factors predisposes this client to developing digoxin toxicity?

The correct answer is A. Taking a high-ceiling diuretic predisposes the client to digoxin toxicity as both medications can cause hypokalemia, which increases the risk of digoxin toxicity. High-ceiling diuretics like furosemide increase potassium excretion, leading to low potassium levels. Digoxin toxicity is more likely to occur in the setting of low potassium levels because digoxin competes with potassium for binding sites on the sodium-potassium pump in cardiac cells. This competition can result in increased digoxin binding to the pump, leading to toxicity. Choices B, C, and D are incorrect because they do not directly affect potassium levels or interact with digoxin in a way that predisposes the client to toxicity.