This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Digitalis has positive inotropic effect by the virtue of its effect on: 
Select and explain. 
A. Na+ K+ATPase pump, B. Na Glucose channels, C. H+K+ ATPase pump, D. Calcium Pump
A: Na+ K+ATPase pump
Answer: A: Na+ K+ATPase pump 
Explanation: None