Final answer:
The equation that shows inverse variation is C) y = 1/x, as it represents a situation where one variable decreases as the other increases.
Step-by-step explanation:
The inverse variation occurs when one variable increases as the other variable decreases at a consistent rate, and is represented mathematically as y = k/x, where k is a nonzero constant. Given this definition, the equation that shows inverse variation among the provided options is C) y = 1/x. The other options given are not representations of inverse variation because they either show a direct variation, or a quadratic relationship or are simply linear equations with a y-intercept. Recognizing the form y = k/x as the defining factor of inverse variation highlights why option C aligns with this concept, distinguishing it from the remaining choices that fail to capture the inverse relationship between variables.