In the attached network diagram, which device is the switch?

 A switch is a network device that connects multiple devices on a local area network (LAN) and forwards data packets between them. A switch can be identified by its icon, which is a rectangle with four curved lines on each side. In the attached network diagram, device D is the switch, as it matches the icon and connects three computers to device A, which is another network device. References:

[What is a Network Switch and How Does it Work?]

[Network Diagram Symbols and Icons | Lucidchart]