What is the command to configure spanning tree in PVST mode?

The command to configure spanning tree in PVST (Per VLAN Spanning Tree) mode is "spanning-tree mode pvst." This command enables the PVST protocol, which allows a separate spanning tree instance for each VLAN. PVST is advantageous in environments with multiple VLANs as it helps manage layer 2 loops and offers better load balancing between redundant links by allowing each VLAN to utilize different paths through the network topology based on the specific spanning tree for that VLAN.

Using this command, a network administrator can ensure that the spanning tree algorithm correctly processes traffic and actively manages how packets are routed through the network, maintaining optimal performance and reducing the risk of loops. The other choices do not accurately enable PVST mode. For instance, setting the RSTP mode or default mode would not achieve the desired configuration of a separate spanning tree instance for each VLAN.