Answer:
D) theory
Explanation:
Theory is the set of fundamental principles of an art or a science. Theory is a synthesized opinion, it is a general notion. From the Greek theoria which in the historical context meant to observe or examine. With its evolution the term came to designate the set of ideas, the basis of a certain theme, which seeks to convey a general notion of some aspects of reality.
Theory is also a conjecture, an opinion formed before a fact. One theory attempts to explain something difficult to accomplish.
A scientific theory is the speculative part of a science, as opposed to practice. It is a consistent system formed by observations, ideas and axioms or postulates, constituting as a whole a set that tries to explain certain phenomena.
Examples of scientific theories are: Chaos Theory, Communication Theory, Knowledge Theory, Evolution Theory, Game Theory, Quantum Theory, Relativity Theory, among others.