Answer:
The best answer for the question: What makes this a scientific theory, when talking about the Big Bang Theory and its acceptance by the scientific community as the best explanation for how the universe originated, would be: It is the best explanation that scientists can offer, based on many scientific investigations.
Step-by-step explanation:
The origins of the universe, how it came to be, whether it was created by someone, or it was just the result of physical laws, is still very much a mystery. However, especially after the start of the twentieth century, many scientists began to wonder about this origin and were, and still are, divided into two possible theories: one known as the steady state theory, and the one that is most favored today, the Big Bang Theory. Given the empirical data and information that has been collected, and from research done by various scientists around the world, applying the different laws that exist, especially Hubble´s Law, and from literally observation of space, today most scientists support the theory of the Big Bang, even if they cannot assure that THAT is precisely how the universe came to be. This is why the answer is the last option.