What is the primary use of Unity's networking libraries?

Unity's networking libraries are primarily designed to implement multiplayer functionality within games. These libraries provide the tools and frameworks necessary for developers to create real-time online experiences, allowing multiple players to interact within the same game world concurrently. This includes features such as synchronization of player actions, managing network connections, and handling data transfer between clients and servers.

By utilizing these networking capabilities, developers can create games that foster engagement through cooperative or competitive play, which is a fundamental aspect of the multiplayer gaming experience.

The other options focus on areas not directly related to networking. Single-player games do not generally rely on networking capabilities, as they are created to function independently of other players. Designing 3D environments is more focused on level creation and asset management rather than network communication. Enhancing graphic fidelity relates to improving visual quality through shaders, lighting, and textures, which also falls outside the scope of networking functionalities.