How many phases can a single ring contain?

A single ring can contain up to four phases, which is why this is the correct answer. In electrical systems, particularly when discussing AC circuits or power distribution, phases represent the different parts of the supply that can distribute electric power.

Typically, a single ring in a multi-phase system can have two phases or more, but four is the standard maximum for many practical applications, such as in multi-phase power generation and transmission systems. Each phase corresponds to a different voltage waveform which aids in balancing loads and minimizing losses in electrical systems.

While other options suggest higher options, such as six or eight phases, these are not commonly implemented in typical single-ring configurations and might pertain to specialized applications or theoretical scenarios that exceed the usual design parameters.