A Credential asset is created by a developer in Orchestrator as seen in the below...

In Orchestrator, when a Credential asset is created and the username value is changed, the password must also be changed to ensure that the credential set remains valid. The username and password are linked as they represent the credential pair used for authentication. Changing one without the other would result in mismatched credentials that cannot be used for logging in to the system that these credentials are associated with. Therefore, the correct answer is D.