The true correct response is:
There is lots of evidence to support it.
Why: Natural selection is considered a scientific theory because it is based on a substantial body of evidence from multiple fields, including genetics, paleontology, and ecology. A scientific theory is an explanation of an aspect of the natural world that is supported by a wide range of empirical evidence and has been rigorously tested and validated over time. In the case of natural selection, evidence from various studies and observations consistently supports the idea that traits which confer a reproductive advantage tend to be passed on to subsequent generations, leading to evolutionary changes within populations. This extensive support distinguishes natural selection as a robust scientific theory rather than a mere hypothesis or opinion.