A scientific theory has to be

a. true.

b. well established and not disputed.

c. accepted by others.

d. testable.

The answer here would be D.

In science the term theory is a bit different than the everyday use of the word theory. In science theory is not a hunch and or an idea that came out of nowhere but an interpretation of the facts that is a product of much rational examination. Theories can change but the facts themselves will not. A trait of a good theory can be its predictability that is that the things will happen how the theory will say it will happen so the theory should be testable.