Which solution will meet these requirements?

Explanations:

This option utilizes Amazon EC2 instances in an Auto Scaling group across multiple Availability Zones, which ensures high availability and scalability. Additionally, using an Amazon RDS DB instance in a Multi-AZ configuration provides automatic failover and backup capabilities, eliminating single points of failure for both the application and database.

This option deploys application servers in a single Availability Zone, which introduces a single point of failure for the application. Although EC2 Auto Recovery can help with instance failures, it does not provide the high availability and resilience required since the database is also on an EC2 instance without redundancy.

While this option uses an Auto Scaling group across multiple Availability Zones, it only employs a read replica in a single Availability Zone. This does not provide the necessary redundancy for the primary database. If the primary DB fails, promoting the read replica would not help if that zone also experiences issues, leading to a potential single point of failure for the database.

Although this option employs an Auto Scaling group across multiple Availability Zones, using EC2 instances for both primary and secondary database servers does not leverage managed database services. Amazon EBS Multi-Attach is not a suitable solution for database redundancy and does not provide the failover capabilities that Amazon RDS offers, leading to potential data loss and single points of failure.