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
[{'content': 'Digitalis has positive inotropic effect by the virtue of its effect on: \nSelect and explain. \nA. Na+ K+ATPase pump, B. Na Glucose channels, C. H+K+ ATPase pump, D. Calcium Pump', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]