16. Which of the following can be termed persistent atrial fibrillation?

A. Acute onset of atrial fibrillation with spontaneous termination 2 days later

B. Atrial fibrillation that has been continuously present for 4 years

C. Atrial fibrillation that is present for 10 days and required electrical cardioversion

D. Atrial fibrillation occurring an average of 5 times weekly eventually requiring antiarrhythmic drug therapy to maintain sinus rhythm