Which of the following is a layer in the TCP/IP model?

• A. Network
• B. Internet
• C. Application
• D. Transport

Answer: (A)

In the TCP/IP model, the data stack is organized into four layers: Application, Transport, Internet, and Network Interface (also called Link or Network Access in some descriptions). The bottom layer, the one that actually handles sending and receiving packets on the physical or local network, is responsible for interfacing with the network hardware, constructing and parsing the frames, and dealing with hardware addresses like MAC addresses. This layer maps to how the IP packets move onto and off the local network medium (Ethernet, Wi‑Fi, etc.) and how they are framed for transmission.

The option identified as the correct layer corresponds to that bottom network-access layer. It captures the responsibility of interfacing with the local network hardware and ensuring data can be transmitted over the physical medium, which is why it’s considered a TCP/IP layer in many models. The other layers—Application, Transport, and Internet—represent the higher-level or routing-related functions and are clearly recognized as layers within TCP/IP as well.