What must be enabled to use external storage credentials?

To use external storage credentials in ServiceNow Discovery, the Discovery External Credential Storage plugin must be enabled. This plugin is specifically designed to facilitate the integration of external credential storage systems with ServiceNow. By enabling this plugin, organizations can securely store and manage credentials externally, which enhances security and simplifies credential management. This capability is crucial for environments where sensitive information, such as passwords, needs to be handled in a secure manner, allowing discoveries to take place without compromising the security of the credentials involved.

The other choices, while related to credential management, do not specifically enable external storage for credentials. The External Credential Management plugin and other listed options may provide various functionalities regarding credential handling but do not directly activate the features related to external storage. Thus, the right answer focuses on the specific requirement for utilizing external storage credentials effectively.