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 acts in CHF by: 
Select and explain. 
A. Na+ K+ ATPase inhibition, B. Na+ K+ ATPase stimulation, C. Blockade of calcium channels, D. Increasing the refractory period of AV node
A: Na+ K+ ATPase inhibition
Answer: A: Na+ K+ ATPase inhibition 
Explanation: None