Which layer is responsible for the physical aspects of transmission, including media, signal, and binary transmission?

• A. Data Link Layer
• B. Transport Layer
• C. Network Layer
• D. Physical Layer

Answer: (D)

The Physical layer handles the actual transmission of raw bits over a physical medium. It covers the hardware aspects that carry the signal—the media itself (copper, fiber, air), how the signal is represented (voltage levels, light, radio), and how bits are timed and encoded for transmission. In short, it deals with turning binary information into something that can travel over physical cables or through space and then back into bits at the other end. The Data Link layer handles framing, MAC addressing, and error detection on a link, the Network layer handles routing and logical addressing across networks, and the Transport layer handles end-to-end reliability and flow control. Because this question emphasizes the media, signaling, and binary transmission aspects, the Physical layer is the correct choice.