Which of the following is a machine-oriented Vault authentication backend?

Okta is an identity provider primarily used for human user authentication, allowing Vault to integrate with existing corporate directories for users, not typically for machine authentication.

The AppRole authentication method provides a secure and programmatic way for machines, applications, and automated processes to authenticate with Vault using Role IDs and Secret IDs, eliminating the need for hardcoded credentials.

Transit is a secrets engine that performs cryptographic operations as a service, not an authentication backend used to verify identities.

GitHub is an authentication backend primarily designed for human users, allowing developers to authenticate to Vault using their GitHub identities.