What action is described as showing or demonstrating an effect?

The term that best describes the action of showing or demonstrating an effect is "impact." In literary and critical contexts, "impact" refers to the strong effect or influence that one element can have on another. When something impacts another, it actively alters or shapes the reality or perception of that element, effectively demonstrating a tangible outcome or consequence.

On the other hand, while "affect" can relate to influencing something, it is more about the change in feelings or psychological state rather than demonstrating an effect outright. "Advance" typically refers to moving something forward or improving a situation rather than illustrating a result. "Highlight," while it can refer to bringing something to attention, suggests emphasis rather than the direct demonstration of an effect. Thus, "impact" is the most suitable term for showing or demonstrating an effect in this context.