Answer:
Option D
Explanation: Theories are used for explaining and understanding a subject matter. For example; the theory of evolution, theory of Einstein on relativity and so on.
A theory is a linked idea use in explaining something - data. There are many advantages of theories(which I am just going to mention few of them. They;
(1). Makes us to identify a problem and plan a solution for it.
(2). They provide concept to name what is obtained or observed