Which feature allows a user to manage or limit bandwidth for applications in RouterOS?

The ability to manage or limit bandwidth for applications in RouterOS is primarily facilitated by queue trees. Queue trees allow for sophisticated traffic management by enabling users to define various queues that can prioritize, limit, or allocate bandwidth based on specific criteria such as source or destination IP addresses, or application types. This granular control helps in efficiently managing network resources and ensuring that critical applications receive the appropriate bandwidth while limiting less important or non-critical traffic.

In contrast, other options like HotSpot are primarily focused on user authentication and access control, rather than bandwidth management. The Firewall is used for securing the network by controlling traffic based on specified rules, but does not directly manage or limit bandwidth for applications. Routing protocols, meanwhile, are designed to determine the best paths for data to travel across the network and do not involve bandwidth management at the application level. Thus, queue trees are the feature specifically dedicated to bandwidth management, making them the correct choice.