Final answer:
A scientific law is a description of a repeating pattern in nature, often expressed as a mathematical equation, that is universally accepted; it describes what happens in the natural world.
Step-by-step explanation:
A scientific law is a rule that describes a pattern in the natural world. The correct answer to fill in the blank is D) scientific law. Scientific laws are concise descriptions, often formulated as mathematical equations, which describe the behavior of an aspect of nature universally. For instance, Newton's second law of motion succinctly relates force (F), mass (m), and acceleration (a) with the equation F=ma. In contrast, a scientific theory is a well-substantiated, comprehensive, and testable explanation of particular aspects of nature. Theories are broader than laws and explain why we observe what we do. An example of a scientific theory is the theory of evolution, which explains the diversity of life on Earth.
It's important to distinguish between a scientific law and other scientific concepts such as a hypothesis, which is a preliminary explanation that can be tested and refined through experimentation and observation. A scientific theory goes beyond a hypothesis because it is substantiated by a significant body of evidence and has withstood rigorous testing.