A company has a multi-tier application that runs six front-end web servers in an Amazon EC2 Auto Scaling group in a single Availability Zone behind an Application Load Balancer (ALB). A solutions architect needs to modify the infrastructure to be highly available without modifying the application. Which architecture should the solutions architect choose that provides high availability?

1. Create an Auto Scaling group that uses three instances across each of two Regions.
2. Modify the Auto Scaling group to use three instances across each of two Availability Zones.
3. Create an Auto Scaling template that can be used to quickly create more instances in another Region.
4. Change the ALB in front of the Amazon EC2 instances in a round-robin configuration to balance traffic to the web tier.