The VP of Marketing wants Sales Reps to get updates when materials are updated in the Marketing library. What feature should an Administrator recommend?

A validation rule enforces data quality by preventing users from saving records that don't meet specified criteria; it does not provide notifications for content updates.

An email alert can be configured (often as part of a workflow rule or flow) to automatically send notifications to specified users or groups, like Sales Reps, when content in the Marketing library is updated.

An approval process routes records through a series of steps for approval by authorized users; it is not designed to notify users about general content updates in a library.

While users can subscribe to records or reports, there isn't a direct 'subscribe' feature on a Marketing library that automatically triggers email alerts for content updates in the way a configured email alert would.