Which migration strategy should the company use?

Explanations:

Rehosting involves moving the application as-is to the cloud without significant changes. This does not align with modernizing the application or converting it into microservices.

Replatforming involves moving to a new platform with minimal changes, but does not focus on the significant architectural changes required for microservices.

Repurchase refers to replacing the application with a commercial off-the-shelf (COTS) product, which is unrelated to converting a monolithic application to microservices.

Refactoring involves re-architecting the application, typically by breaking it into microservices. This is the most suitable approach for modernizing the monolithic application and moving it to AWS.