This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S., Subject name: Medicine
Digitalis toxicity aggrevated by: 
Select and explain. 
A. Hypokalemia, B. Hyperkalemia, C. Hypocalcemia, D. Hypermagnesemia
A: Hypokalemia
Answer: A: Hypokalemia 
Explanation: (Hypokalemia): Ref: 1375 -H(1433-H17th)DIGITALIS INTOXICATION: - Serious and potentially fatal complication* Advanced age* Renal insufficiency* Acute MI* Hypokalemia* Hypomagnesemia* Hypoxemia* Hypercalcemia* The most frequent disturbance of cardiac rhythm are ventricular premature beats, bigeminy, ventricular tachycardia and rarely ventricular fibrillation.* AV block and nonparoxysmal atrial tachycardia with variable AV block are characteristic of digitalis intoxication.* The Dose of digitalis should be reduced by half in Quinidine, veropamil, amiodarone and propafenone