If a brief example will not clearly explain a point for audience members, then it should be expanded into which of the following?

The most suitable choice is illustration, as it allows for a more detailed and vivid explanation of the point being made. An illustration typically involves a story or a descriptive example that helps to clarify and enrich a concept, making it more relatable for the audience. When a brief example does not suffice in conveying the message clearly, expanding it into an illustration can provide context, engage the audience's imagination, and foster a better understanding of the idea or argument being presented. This method is particularly effective because it can evoke emotions and create visual images that enhance retention and comprehension.

While other options like statistics or testimony might provide supporting data or endorsements, they don't inherently expand upon the initial example in a narrative way, which is what is necessary for clearer understanding in this case. Evidence can refer to various forms of data or support but lacks the narrative quality that an illustration provides. Thus, when clarity and engagement are key, utilizing an illustration effectively enhances the communication of the point.