Final answer:
Digoxin (Lanoxin) is the drug among the listed options that is used to treat congestive heart failure by strengthening heart muscle contractions and managing arrhythmias.
Step-by-step explanation:
The drug used to treat congestive heart failure from the options provided is a. Digoxin (Lanoxin). Digoxin works by increasing the strength of heart muscle contractions, which can be beneficial in treating heart failure. It also helps to slow certain types of irregular heartbeat, particularly atrial fibrillation. This makes it a valuable drug in managing symptoms of heart failure, especially when the patient isn't responding well to ACE inhibitors and diuretics.
Other drugs listed, such as diuretics, might also be used in the context of heart failure to manage fluid retention and hypertension, but based on the choices provided, Digoxin is the most directly associated with treating the condition of congestive heart failure.