Which statement describes a MAC sublayer capability for a shared medium?

• A. Provides a mechanism to allow multiple devices to communicate over a shared medium.
• B. Enables IPv4 and IPv6 to utilize the same network interface.
• C. Places information identifying network layer protocol in the frame.
• D. Implements a trailer to detect transmission errors.

Answer: (A)

When a network uses a shared medium, the MAC sublayer handles access control to let multiple devices send and receive data without trampling each other. It provides the mechanism for coordinating transmissions on that shared channel—think of how classic Ethernet uses listen-before-talk and collision detection (CSMA/CD) to allow many hosts to communicate on the same cable. By managing who can send and how frames are placed on the medium, the MAC sublayer enables multiple devices to share the same medium effectively, with frames addressed to the correct recipient on that shared channel.

The other statements describe aspects not directly about sharing access: enabling IPv4 and IPv6 on the same NIC is about the network layer and host stack; placing the network-layer protocol identifier in the frame is about frame formatting to indicate payload type; and implementing a trailer for error detection is about integrity, not how access to the medium is coordinated.