Which solution achieves this goal?

Explanations:

Using EC2 instances in a single Availability Zone minimizes latency because instances in the same AZ are connected via a low-latency, high-bandwidth network. This configuration reduces the distance data must travel, ensuring faster communication between instances.

Using EC2 instances in multiple AWS Regions increases latency because data must travel over the internet or through inter-region links, which can introduce significant delays due to the longer physical distance and varying network conditions.

Using EC2 instances in multiple edge locations may not effectively minimize latency for internal communications between instances, as edge locations are designed for content delivery and caching rather than for direct instance-to-instance communication.

Using EC2 instances in the same Availability Zone but in different AWS Regions is not possible, as instances cannot exist in multiple regions simultaneously. Even if interpreted as instances in different AZs within a single region, it would still introduce more latency than using instances in the same AZ.