In Treating a Patient with Congestive Heart Failure, You Have

In treating a patient with congestive heart failure, you have prescribed digoxin (a cardiac glycoside) to strengthen the heart's output and maintain a regular rate. The target of this drug is the

A) ATP synthase.
B) Na⁺, K⁺ - ATPase.
C) ligand - gated Ca²⁺ channel.
D) resting K⁺ channel.
E) voltage - gated Na⁺ channel.