Which layers are primarily concerned with moving raw data?

The correct choice identifies the lower four layers of the OSI (Open Systems Interconnection) model, which are specifically tasked with the transmission and movement of raw data throughout a network. These lower layers include the Physical layer, Data Link layer, Network layer, and Transport layer.

The Physical layer is responsible for the actual physical connection and transmission of raw bit streams over a physical medium. The Data Link layer ensures reliable transmission of data frames between two nodes connected on the same physical medium. The Network layer handles the routing and forwarding of data packets across different networks, deciding the best path for data to travel. Lastly, the Transport layer provides end-to-end communication services, ensuring complete data transfer between hosts.

Understanding these lower layers is crucial in networking as they focus on the actual moving of data bits and maintaining the integrity and flow of that data across the respective networks. This comprehensive role they play in handling and moving raw data sets them apart from the upper layers, which deal more with data format, session management, and application-specific interactions.