Which VLANs are defined on the local switch and not shut down?

The VLANs defined on a local switch that are not shut down play a crucial role in ensuring that network traffic flows correctly across the various segments of a network. In this case, the combination of VLAN 1, VLAN 10, and VLAN 20 indicates that these VLANs are active and can be utilized for data transmission on the switch.

VLAN 1 is the default VLAN on most switches and is typically designated for management purposes. While it is common for VLANs to be configured, they may also be administratively disabled (shut down) to prevent traffic from flowing through them. Therefore, identifying VLANs that are both defined and operational is essential for network management.

VLANs 10 and 20 are also specified as part of this answer, which aligns with typical subnetting practices where multiple VLANs are deployed to segment network traffic for improved performance and security. By choosing this specific set of VLANs, it indicates a focus on managing traffic effectively while avoiding disruptions caused by inactive VLANs.

The other options do not include VLANs that are typically defined and operational in a standard switch configuration context. That means the specifically chosen option stands out as the most accurate for identifying VLANs that are actively being utilized on the switch.