This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pharmacology
Digoxin toxicity is aggravated by? 
Select and explain. 
A. Hypokalemia, B. Hyperkalemia, C. Hypercalcemia, D. Hypocalcemia
B: Hyperkalemia
Answer: B: Hyperkalemia 
Explanation: Digoxin toxicity causes hyperkalemia, or high potassium. The sodium/potassium ATPase pump normally causes sodium to leave cells and potassium to enter cells. Blocking this mechanism results in higher serum potassium levels (REF.Essentials of medical pharmacology K D TRIPATHI 8th Edition)