Which of the following is a representative standard for OSI Layer 1?

The correct answer, EIA-232, is a representative standard for OSI Layer 1, which defines physical layer specifications for serial communication. This standard specifically outlines the electrical characteristics and signaling for serial cables and connectors, establishing how signals are transmitted over physical media.

Layer 1 of the OSI model is focused purely on the physical aspects of network communications, such as the types of cables, electrical signals, and the physical interface that connects devices. EIA-232, also known as RS-232, is primarily concerned with the physical connection, voltage levels, and timing required for data transmission.

Other options, while they play significant roles in networking, do not focus exclusively on the physical layer. IEEE 802.1X pertains to network access control (Layer 2), detailing authentication protocols rather than the physical transmission medium. PPP, or Point-to-Point Protocol, operates at the data link layer (Layer 2) and handles the framing and addressing of data packets, thus not aligning with the physical layer requirements. Ethernet II, while related to Ethernet technology, is primarily associated with Layer 2 functionality, dealing with how data packets are formatted and addressed but not the physical transmission specifications themselves.