Which word best describes observable occurrences or circumstances?

The correct choice, which is "Phenomena," aptly describes observable occurrences or circumstances. This term is commonly used in various scientific and academic contexts to refer to events or facts that can be perceived through our senses or measured, and that are often studied to derive conclusions or gain understanding.

Using “phenomena” emphasizes real and tangible aspects of the world that can be observed or experienced, making it a fitting descriptor for anything that manifests in reality.

The other options do not capture this meaning effectively. "Hypotheses" refers to proposed explanations made on the basis of limited evidence as a starting point for further investigation but does not pertain to actual occurrences. "Fictions" denotes imaginary events or narratives that are not real, and "Abstracts" typically refer to concepts that are not tied to specific instances or observable reality, focusing instead on ideas rather than physical phenomena. Hence, "phenomena" stands out as the most accurate term for observable events or situations.