The drug of choice for treatment of CHF (Congestive Heart Failure), especially in the case of atrial fibrillation, is C. Cardiac glycosides.
Cardiac glycosides, such as digoxin, are medications that help to increase the strength and efficiency of the heart muscle's contractions. They are often used to treat CHF and other heart conditions, especially when there is atrial fibrillation present.
ACE inhibitors (A) and beta-blockers (D) are also commonly used to treat CHF, but they are not the drug of choice in the case of atrial fibrillation. Diuretics (B) are often used to help manage the fluid buildup that can occur with CHF, but they do not directly treat the condition itself.