What command enables rapid PVST mode on a switch?

The command that enables Rapid Per VLAN Spanning Tree (PVST) mode on a switch is correctly identified as "spanning-tree mode rapid-pvst." This command configures the switch to utilize the Rapid PVST+ protocol, which is an enhanced version of the original PVST, designed to provide faster convergence times in network topologies.

Rapid PVST+ improves upon traditional Spanning Tree Protocol (STP) by reducing the time taken to detect links that are down and subsequently re-establishing active paths in the network. The command specifically tells the switch to operate under this mode, which is essential for ensuring efficient handling of network changes and redundancy.

Understanding the context of the other options helps clarify why they do not apply in this scenario. For example, "enable spanning-tree rapid-pvst" is not a valid command for configuring the switch. Similarly, "set spanning-tree mode rapid-pvst" does not match the syntax required by Cisco IOS to make the configuration change. Lastly, "configure rapid-pvst" lacks the proper command structure necessary to enable the feature on a switch. Therefore, the correct choice is the one that uses the precise syntax recognized by Cisco IOS for activating Rapid PVST.