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
The positive inotropic effect of digitalis is due to inhibition of Na+/K+ ATPase pump in cardiac muscle cell membrane leading to: 
Select and explain. 
A. Decreased activity of Na+/Ca++ exchanger causing decreased influx of sodium and decreased efflux of Ca++ in the sarcolemma, B. Decreased efflux of Na+ leading to less negative resting membrane potential and opening of voltage gated Ca++ channels on the T tubules, C. Increased intracellular Na+ causing increased efflux of Na+ and increased influx of Ca++  through Na+/Ca++ exchanger in the sarcolemma, D. Increased intracellular Na+ decreasing the activity of Ca++ pump in the sarcoplasmic reticulum
A: Decreased activity of Na+/Ca++ exchanger causing decreased influx of sodium and decreased efflux of Ca++ in the sarcolemma
Answer: A: Decreased activity of Na+/Ca++ exchanger causing decreased influx of sodium and decreased efflux of Ca++ in the sarcolemma 
Explanation: None