How do CSMA/CD and full-duplex switches influence collision domains?

• A. Full-duplex eliminates collisions on a switch port.
• B. CSMA/CD applies to wireless networks only.
• C. CSMA/CD applies to shared media; switches create a separate collision domain per port; full-duplex eliminates collisions.
• D. A collision domain expands with more switch ports.

Answer: (C)

Collision domains are the network segments where two devices might transmit at the same time and cause a collision. CSMA/CD is the method Ethernet uses on a shared medium with half-duplex to detect those collisions and back off. On a network that uses a hub or coax, all devices share one collision domain, so collisions can happen among any of them.

A switch changes that picture. Each port on a switch is its own separate link to a device, so each port creates its own collision domain. There’s no shared medium across multiple devices on a single port.

When a link operates in full-duplex, transmissions can go in both directions simultaneously, and there’s no collision because there isn’t a single shared channel to collide on. So full-duplex on switch ports effectively eliminates collisions on those links.

Putting it together: CSMA/CD applies to shared media; switches create a separate collision domain per port; and full-duplex eliminates collisions. The other ideas miss one or more of these pieces, which is why this combination best explains how collision domains are influenced.