Which statement about media access control is accurate?

• A. Data link layer protocols define the rules for access to different media.
• B. It is responsible for error-correcting data at the transport layer.
• C. It defines routing between networks.
• D. It performs data compression for transmission.

Answer: (B)

Access to the shared medium is controlled by the data link layer, specifically the MAC sublayer, which defines how devices coordinate transmissions and how they are addressed on that medium. Different media have different MAC rules (for example, CSMA/CD in traditional Ethernet and CSMA/CA in Wi‑Fi), so saying that data link layer protocols define the rules for access to different media is accurate. Other activities mentioned—error correction at the transport layer, routing between networks, and data compression—aren’t handled by the MAC layer. Error handling across transport is end-to-end (not MAC), routing is a network-layer function, and compression isn’t a MAC responsibility.