Which AWS service should the company use to meet this requirement?

Explanations:

AWS WAF (Web Application Firewall) is used to protect web applications from common web exploits and does not manage or monitor IAM access keys.

AWS Shield is a managed DDoS protection service and is not related to IAM access key management or rotation.

Amazon Cognito provides user authentication and identity services but does not have functionality to check or manage IAM access key rotation.

AWS Trusted Advisor is a resource that provides real-time guidance to help provision your resources following AWS best practices, including checks for IAM access key rotation and identifying keys that have not been rotated recently.