Which AWS service gives users the ability to combine existing accounts into a centrally managed hierarchy?

Explanations:

AWS Organizations allows users to create and manage multiple AWS accounts in a hierarchical structure, enabling centralized management of billing, access, and policies.

AWS Identity and Access Management (IAM) is primarily focused on managing user access and permissions within a single AWS account, not on managing multiple accounts.

AWS Config is a service that enables you to assess, audit, and evaluate the configurations of your AWS resources, but it does not manage multiple accounts or create a hierarchy.

Amazon Inspector is a security assessment service that helps improve the security and compliance of applications deployed on AWS, but it does not provide account management features.