The correct answer isBbecause the company wantshigh availability,minimum downtime,minimum data loss, and theleast operational effort. For the application tier, configuring the Auto Scaling group to spanmultiple Availability Zonesincreases resilience by ensuring that the loss of one Availability Zone does not make the application unavailable. Since the application is already behind an Application Load Balancer, traffic can continue to be routed to healthy instances in other Availability Zones.

For the database tier, the single-AZ Aurora PostgreSQL deployment represents a single point of failure. Configuring the database forMulti-AZimproves availability and durability by maintaining a synchronized standby in another Availability Zone and supporting failover with minimal disruption. This approach is aligned with AWS best practices for relational database high availability.

UsingAmazon RDS Proxyfurther improves availability at the application layer by managing database connections efficiently and helping applications reconnect more quickly during failover events. This reduces the operational complexity of handling transient database interruptions and can improve application resilience.

Option A introduces multi-Region complexity, which is not required to meet the stated need and creates more operational overhead. Option C does not provide high availability because snapshots are a backup and restore mechanism, not an automatic failover solution, and hourly snapshots can result in significant data loss. Option D is unnecessarily complex and changes the application data flow in a way that is not needed.

The simplest and most AWS-aligned solution is to make both the compute and database layers highly available acrossmultiple Availability Zones. That provides resilience with the least operational burden.