Which AWS service should the system administrator use to identify who made this change?

Explanations:

Amazon Inspector is a security assessment service that helps improve the security and compliance of applications deployed on AWS, but it does not provide logging or auditing capabilities to track user actions in the AWS account.

Amazon Pinpoint is a marketing communications service that allows businesses to engage with their customers. It does not have functionalities for tracking changes made to AWS resources or identifying users who made those changes.

AWS CloudTrail is a service that enables governance, compliance, and operational and risk auditing of AWS accounts. It records API calls made in the account, allowing administrators to determine who made a change, such as terminating an EC2 instance, by reviewing the logs.

AWS Trusted Advisor is a service that provides real-time guidance to help provision your resources following AWS best practices. It does not track user actions or changes made to AWS resources, thus is not suitable for identifying who made specific changes.