Correct option is C
If symptomatic bradycardia persists after atropine, next step is temporary pacing (transcutaneous → transvenous).
Explanation of options: (a) ✘ Cardioversion is for tachyarrhythmias, not bradycardia. (b) ✘ Amiodarone treats tachyarrhythmias, not bradycardia. (c) ✔ Correct; transvenous pacing is the definitive management. (d) ✘ Adenosine is for supraventricular tachycardia, not bradycardia.