Which of the following describes a cloud service that provides a vault access policy?

A cloud service that provides a vault access policy is best described by Amazon S3 Glacier vault. Amazon S3 Glacier is designed for data archiving and long-term storage, and it includes vaults where you can store your data. Each vault in S3 Glacier allows you to define an access policy, which specifies who can access the vault and what actions they can perform. This feature is critical for managing sensitive or important data, ensuring that only authorized users have the ability to access or manage the stored information.

Other options relate to different types of services. For example, Amazon RDS (Relational Database Service) is primarily focused on database management and does not offer vaults or specific vault access policies. Amazon EBS (Elastic Block Store) provides block-level storage for use with Amazon EC2 instances, and AWS Lambda allows you to run code in response to events without provisioning servers; neither of these services includes a vault structure that features specific access policies like those seen in S3 Glacier.