Twelve hours after being admitted to the hospital for an inferior wall myocardial infarction, a 65-year-old woman begins to present with dyspnea, dizziness, and syncopal episodes that last a few seconds. Her pulse is 45 bpm. An ECG is shown. Which of the following is the most likely diagnosis?

Lead I
A. First-degree atrioventricular block
B. Multifocal atrial tachycardia (MAT)
C. Mobitz type I block
D. Sinus bradycardia
E. Mobitz type II block
F. Third-degree atrioventricular block
G. Atrial fibrillation