Which of the following is considered an advanced feature in Gmail?

The correct answer focuses on the advanced feature of multiple inboxes in Gmail. Multiple inboxes allow users to configure their email layout in a way that displays multiple sections or panels within the Gmail interface. This feature enhances productivity by enabling users to view specific sets of emails simultaneously—such as unread messages, starred emails, or emails from particular contacts—without having to navigate through their entire inbox.

While the unread message icon, email threads, and labels are useful features, they are more foundational aspects of email management in Gmail rather than advanced capabilities. The unread message icon simply indicates messages that have not yet been read, while email threads allow related messages to be grouped together for easier navigation. Labels provide a way to categorize and organize emails but do not enhance the interface layout like multiple inboxes do. Thus, the ability to create a customized workspace with multiple inbox sections represents a higher level of usage and organization within Gmail.