Which attribute specifies the instance ID in a portlet configuration?

The instance ID is a crucial component in portlet configuration as it uniquely identifies an instance of a portlet within a portal page. This is particularly important when the same portlet is deployed multiple times on the same page. The instance ID attribute allows the portal to distinguish between different instances of a portlet.

When a portlet is defined, the instance ID provides a way to maintain separate states and configurations for each instance. This means that user interactions with one instance do not affect another instance of the same portlet. The instance ID is automatically generated and is configured in the portlet's deployment descriptor, ensuring that it is unique and functional within the user interface context.

In contrast, attributes such as defaultPreferences, persistSettings, and settingsScope serve other purposes in portlet configuration, such as defining default user preferences, determining how user settings are retained, or establishing the scope of settings (e.g., application-wide or user-specific). None of these attributes specifically denote the distinct identity of a portlet instance, which makes the instance ID the right answer for this question.