When you are asked to mention theories and you mention Natural selection, it looks like you have struck some chords and you are wrong but that's not true, actually you are right and you are just dealing with science. You see, unlike English language, Scientist have different meanings and understanding for words like Fact, Hypothesis, Theory, and Law. So what do they mean to a scientist compared to a random Joe?
Coming to a scientist, Facts are just observations about the things around our world. Things like day and night that happens regularly and we know that they are normal circumstance that we just find explanations to so we understand them. They do not need too much work to be done with them.
When it comes to hypothesis, there need to be a test done. With hypothesis, it isn't about proving, it is about testing and further investigation. There are usually multiple hypothesis to explain an observation and when this is done, the wrong ones or the one that do not meet the explanations are cancelled out. This doesn't mean that the one left is a theory or a law, it is just a possible explanation to a phenomenon or test. The existing hypothesis can still lead to more hypothesis that can either agree or disagree with the original one.
Hypothesis can be a long journey to nowhere but when a lot of hypothesis meet the check mark, then they can all be summed up to become a theory. It is a result of well substantiated explanations which were acquired through scientific methods and repeated testing that were confirmed through observation and experimentation. These theories can be used to predict how a thing was and how it would be since it has been confirmed by numerous experiments and observations.
A very good way to look at this is with an example of a FACT that people fall sick in their lifetime, but we can then hypothesize that objects either living or bad gets into their body and make them fall sick. With this hypothesis we begin to do several test, experiments, and observation such as looking at Putrid humors, demonic possession of the body, sunspot, glutten, germs, or chemical as things that could get people sick. Cancellation begins and we are left with germs so we could agree that the Germ Theory of disease did well.
Through out our lifetime, we have come to the fact that Evolution happened and happens but how did this fact come? We look at numerous hypothesis on how living things change over time, and we have discarded a lot of bad ones to come up with the theory of Evolution by Natural Selection which has helped us explained how organism can evolve over time. This theory has passed a lot of test and it can be used to predict what happened in the past or what would happen in the future.
When you hear theory, one thing you always hear in science is LAW. In science, laws are statements based on repeated experimental observations that describes phenomenons in nature using Mathematics to explain how it happens but not why it happens. For instance the Law of gravity that states states that the force acting on a body is equal to the rate of change of the body's momentum. This is a law, it explains how gravity occurs but not why it occurs but with gravity so it is also a theory.
Newtons law of Universal Gravitation explains how two objects will attract themselves based on mass and distance and Newton solved this mathematically with F1 = F2 =Gm1 X m2/r2 but this doesn't describe why, and to do so, the theory of gravity is looked at. For theory to occur, there are hypothesis such as force pulling on the object, Structure of the Universe making things fall, The earths ground surface works with magnetic field making this objects fall towards it. When we look at this hypothesis and remove the bad ones we are left with Einstein Theory of Gravity called General Relativity.
Back to the theory checking tests, experiments and observation, scientist after seeing quantum mechanics realized that the theory of Einstein didn't account for the smallest gravitational scales in the universe, so we still hold on to the theory but work on it to see how it can be modified when other lists are checked in the quantum level. With science, it is a continuous journey of learning, unlearning, and relearning.
Reference
https://study.com/academy/lesson/what-is-the-scientific-theory-definition-characteristics-example.html
https://courses.lumenlearning.com/suny-hccc-research-methods/chapter/chapter-4-theories-in-scientific-research/
https://www.tandfonline.com/doi/full/10.1080/03080188.2022.2150807
https://pdf.sciencedirectassets.com/277811/1-s2.0-S1877042813X00278
https://study.com/academy/lesson/what-is-a-scientific-law-definition-examples-quiz.html
https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Introductory_Chemistry
https://plato.stanford.edu/entries/laws-of-nature/
