For most of the first 1,800 years in the common era, most people, including scholars, did not believe in sexual or asexual reproduction for many organisms. They thought many creatures, including frogs and mice, came from nonliving things. This was the theory of spontaneous generation. For example, maggots were believed to simply appear in meat as it spoiled. Today we know that maggots come from eggs that were laid on or in the meat by their mothers. Louis Pasteur proved that living organisms do not just appear. Broth that is left sitting out for a while will grow cloudy as small organisms live and grow in it. Louis Pasteur boiled broth and let it cool without coming into contact with any "particles" in the air. Broth treated that way did not grow cloudy.

Louis Pasteur's experiment showed that small organisms that live in broth do not come from the broth itself. Which of the following best describes this statement and how it changed what scientists know?
A.
It is a scientific theory of how life begins that fits the facts better than spontaneous generation.
B.
It is a scientific observation that goes against the theory of spontaneous generation, so the theory must be wrong.
C.
It is a set of detailed observations of how single-celled organisms live and reproduce.
D.
It is a result that was predicted by the theory of sexual reproduction, proving that theory to be correct.