AWS CloudTrailis a service that enables governance, compliance, and operational and risk auditing of your AWS account. With CloudTrail, you can log, continuously monitor, and retain account activity related to actions across your AWS infrastructure. CloudTrail logs provide a history of AWS API calls for your account, including those made by the AWS Management Console, AWS SDKs, command-line tools, and other AWS services. In this case, AWS CloudTrail will help the administrator identify which user deleted the resources by reviewing the event history that records details such as which user performed the action, the time of the action, and which resources were affected.

B. Amazon Inspector: Incorrect, as it is a security assessment service that helps identify vulnerabilities and deviations from best practices, not for tracking user activity.

C. Amazon GuardDuty: Incorrect, as it is a threat detection service that monitors malicious activity and unauthorized behavior, not specifically for tracking changes made by users.

D. AWS Trusted Advisor: Incorrect, as it provides best practices and guidance for cost optimization, security, fault tolerance, and performance, not for logging user actions.

AWS Cloud References:

AWS CloudTrail