Which layer of the OSI model is represented by physical cables and electromagnetic signals?

The correct answer is the Physical Layer. This layer is responsible for the transmission and reception of unstructured raw data over a physical medium, which includes the actual cables, radio frequencies, and other forms of media involved in data transmission. It defines the physical characteristics of the hardware involved, such as voltage levels, timing of voltage changes, physical data rates, the maximum transmission distances, and the layout of pins, sockets, and cables.

In essence, the Physical Layer covers the tangible aspects of network communication, which means it deals with the electromagnetic signals that carry data across the network infrastructure. By establishing the standards for the physical transmission of data, it provides the foundation for the layers above it, allowing for reliable communication in the higher layers of the OSI model.