Which of the following best illustrates a sophisticated demeanor?

A sophisticated demeanor is characterized by refinement, elegance, and a polished manner of interaction. The term "urbane" specifically refers to someone who is suave, courteous, and well-mannered, embodying the qualities that suggest sophistication. This type of demeanor often manifests in social situations where charm and cultural awareness enhance one’s presence.

In contrast, while "witty" describes someone with a quick and inventive sense of humor, it does not inherently convey the refinement associated with sophistication. "Sullen" indicates a moody, sulky, or gloomy disposition, which starkly contrasts the poised and graceful qualities of a sophisticated demeanor. "Vigor," on the other hand, pertains to physical strength or energy, lacking the social polish that is essential to a sophisticated demeanor. Thus, "urbane" is the only choice that encapsulates the essence of sophistication effectively.