A 65-Year-Old Woman Had the Following Electrocardiogram Recorded at Her

A 65-year-old woman had the following electrocardiogram recorded at her annual physical. She reported to her doctor that sometimes her pulse rate feels a little irregular. Standard limb lead III is shown. What is her likely diagnosis?

A) Atrial paroxysmal tachycardia
B) First-degree atrioventricular block
C) Second-degree atrioventricular block, Mobitz type I (Wenckebach)
D) Normal sinus rhythm
E) Third-degree atrioventricular block