The Open Systems Interconnection (OSI) is a conceptual model whose purpose is to make networks more manageable. Its objectives include allowing for more portable hardware and software integration, the creation of standard interfaces that would allow manufacturers of different systems to interconnect their equipment and the creation of a model that would be used world-wide. There are seven layers to the OSI. The lowest - or first - layer allows a contiguous sequence of bits to be transmitted through the network. Which is the first layer: A. data-link layer, B. physical layer, C. network layer, D. transport layer