What is defined as a systematic explanation for observations in a specific aspect of life?

A theory is defined as a systematic explanation for observations in a specific aspect of life because it provides a well-substantiated explanation of some aspect of the natural world that is based on a body of evidence and can be tested through research. Theories integrate and generalize many hypotheses to develop a coherent understanding of phenomena, thus enabling researchers to predict future events or behaviors related to that aspect of life. They are grounded in inference and can evolve over time as new evidence emerges.

In contrast, a hypothesis is a specific, testable prediction derived from a theory, typically focusing on a narrower aspect of the same phenomena. A research question is more about the inquiry itself rather than the explanation; it guides the research process but does not encapsulate a broader explanation. A variable, on the other hand, is an element that can change and be measured in a study, but it does not provide an explanation by itself. Therefore, the definition aligns with the characteristics of a theory, making it the correct choice for this question.