When requesting SSH access to a remote system, a user accidentally emailed the id_rsa key to the administrator. Which of the following should the user do NEXT?

ssh-add loads a private key into the SSH authentication agent for use in the current session and has no effect on known_hosts or on the compromised key.

Setting chmod 600 on the remote system only corrects file permissions there and does nothing to address the fact that the private key was already exposed by email.

Deleting the local copy and sending id_rsa.pub fixes the process going forward but does not revoke or replace the already-compromised private key, leaving the original key pair a security risk.

The id_rsa file is the private key, which must never leave the owner's possession. Because it was transmitted insecurely via email, it is now compromised and must be treated as untrusted. The user must stop using the exposed key pair and run ssh-keygen to generate a fresh key pair, then register the new public key with the administrator.