Which policy or resource should the company use to meet these requirements?
An Amazon Route 53 simple routing policy
An Amazon Route 53 multivalue answer routing policy
An Application Load Balancer in one Region with a target group that specifies the EC2 instance IDs from both Regions
An Application Load Balancer in one Region with a target group that specifies the IP addresses of the EC2 instances from both Regions
Explanations:
A simple routing policy only routes traffic to a single record, and it does not provide the capability to route traffic based on health checks or across multiple Regions.
A multivalue answer routing policy can distribute traffic to multiple records (such as multiple Regions) and provides automatic health checks. If one Region becomes unhealthy, it stops routing traffic to it.
An Application Load Balancer cannot route traffic to EC2 instances in multiple Regions using a target group with EC2 instance IDs. Target groups are confined to a single Region.
An Application Load Balancer can only use target groups within a single Region. Using IP addresses for EC2 instances in different Regions is not supported in this configuration.
I classify that the answer is:
An Amazon Route 53 multivalue answer routing policy
I guess:
An Amazon Route 53 multivalue answer routing policy