A Database Specialist is setting up a new Amazon Aurora DB cluster with one primary instance and three Aurora Replicas for a highly intensive, business-critical application. The Aurora DB cluster has one medium-sized primary instance, one large-sized replica, and two medium sized replicas. The Database Specialist did not assign a promotion tier to the replicas.
In the event of a primary failure, what will occur?

A. Aurora will promote an Aurora Replica that is of the same size as the primary instance
B. Aurora will promote an arbitrary Aurora Replica
C. Aurora will promote the largest-sized Aurora Replica
D. Aurora will not promote an Aurora Replica