A well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation or experiment.

• A. Hypothesis
• B. Theory
• C. Observation
• D. Tools of Science

Answer: (B)

A scientific theory is a well-substantiated explanation of natural phenomena, built from a large body of facts repeatedly confirmed through observation and experiment, and it provides testable predictions about how the natural world works. This makes it more robust than a simple guess, because it integrates diverse evidence into a coherent account that can be used to anticipate new findings. The explanation isn’t just a single observation; it ties together many lines of evidence and explains why they fit together.

If you look at the other terms, a hypothesis is an educated guess that scientists test through experiments and observations to determine whether it holds, rather than a comprehensive explanation built from extensive evidence. An observation is just noticing and recording facts, not explaining why they occur. Tools of science are the instruments and techniques used to collect data, analyze results, and test ideas, but they aren’t explanations themselves.