From the options provided, the most accurate inference about most science fiction stories is:
They speculate on a world that might be possible one day.
Science fiction often explores future technologies, societal changes, and the implications of scientific advancements, allowing for speculation about what could be possible or plausible in the future. While some stories may include imaginative elements or alternate realities, the core aspect of science fiction usually revolves around exploring possibilities based on current scientific knowledge and theories.