Which of the following best exemplifies a subculture?

The choice highlighting a group with distinct values and norms that differentiate them from the larger culture accurately illustrates what a subculture is. Subcultures exist within the broader cultural context but maintain unique beliefs, practices, and lifestyles that set them apart from the dominant culture. This differentiation can manifest in various forms, such as music preferences, fashion, language, and social behaviors.

In the context of sociology, subcultures allow for the expression of alternative identities and can often emerge as a response to the mainstream culture's norms. Examples include goths, punk rockers, and various youth subcultures that emphasize individuality and difference while still being part of the larger societal framework.

The other options do not fully encapsulate the essence of a subculture. For instance, a mainstream group reflecting societal norms does not exhibit the distinct characteristics that define a subculture. Similarly, an emerging trend accepted by society at large suggests conformity, rather than the divergence of values seen in subcultures. Lastly, a culture that is historically rich and exclusive may indicate a specific tradition or elite status but does not inherently denote the distinct values and norms that characterize subcultures in contrast to the dominant culture.