An application is trying to use a dynamic secret in which the lease has expired.

Comprehensive and Detailed in Depth Explanation:

Once a dynamic secret’s lease expires, it cannot be renewed or reused; a new secret must be requested. The HashiCorp Vault documentation states: "A lease must be renewed before it has expired. Once it has expired, it is permanently revoked and a new secret must be requested." This means that after expiration, the secret is invalidated, and the application must obtain a new secret with a new lease to regain access.

Trying an expired secret (A) is futile as it’s revoked. Performing a lease renewal (B) is impossible post-expiration, as the docs note: "Renewal must occur before the lease expires." Extending the TTL (D) isn’t an option for an expired lease. Thus, C is the correct action.