What should you use to configure this?

Explanations:

An Elastic Load Balancer (ELB) is used to distribute incoming traffic across multiple instances to ensure high availability and fault tolerance. It does not determine which instances to terminate during scaling operations.

A termination policy in Auto Scaling allows you to define the criteria for which instances should be terminated first when scaling in. This can include options such as terminating instances with the oldest launch configuration or the least number of connections.

An IAM role is used to manage permissions and access for AWS services and resources. It does not play a role in the decision-making process for terminating instances in Auto Scaling.

Another scaling group would not directly influence which instances are terminated. Each Auto Scaling group manages its own instances and termination policies; thus, having another scaling group does not determine termination order for the current group.