Which AWS service can securely store Amazon RDS credentials and automatically rotate database user passwords on a scheduled basis?

AWS Secrets Manager is the correct choice because it is specifically designed for securely storing and managing secrets like database credentials, API keys, and other sensitive information. It offers features such as automatic rotation of secrets, including Amazon RDS database credentials, on a scheduled basis, enhancing security by regularly changing access keys. Amazon S3 is an object storage service and is not designed for secret management or rotation. AWS Systems Manager Parameter Store can store secrets, but it does not natively support automatic rotation of database credentials. AWS CloudTrail is a logging and auditing service that records API calls and events, not a secret management service.