To adjust the VLAN configuration, the technician needs to configure the switch. VLANs are configured on switches to segment network traffic logically, even if the devices are connected to the same physical network. By adjusting the VLAN settings on the switch, the technician can ensure that the sales department has access to the marketing department's network resources.

C. Switch: VLANs are configured on switches to logically separate or combine network segments.

Why the other options are incorrect:

A. Network card: A network card is a hardware component that connects a device to a network, but it does not configure VLANs.

B. Patch panel: A patch panel is used to organize and manage network cables but does not play a role in VLAN configuration.

D. Server: A server may host resources, but VLANs are managed at the switch level.

E. Hub: A hub is a basic networking device that simply forwards traffic; it cannot be used to configure VLANs.

This falls under the Networking domain in the CompTIA A+ Core 1 exam​.