Final answer:
A phenomenon that has been rigorously tested and to which there are no known exceptions is called a theory. Hence the correct answer is option D
Step-by-step explanation:
A phenomenon that has been rigorously tested and to which there are no known exceptions is called a theory. A theory is a well-substantiated explanation of an aspect of the natural world that has been supported by multiple experiments and observations. It is more than just a hypothesis, which is a tentative explanation that is yet to be tested.
Hence the correct answer is option D