12) in developing the cell theory, virchow proposed the idea that cells come from pre-existing cells. this was contradictory to the beliefs of most scientists at the time. louis pasteur provided proof of this when he performed an experiment with sterilized nutrient broth. the broth in straight neck flasks grew bacteria, but the flasks with curved necks did not grow bacteria. how are scientific theories formed? a) from the opinions of very educated people b) from one experiment of a famous scientist c) from evidence gained by many experiments of many scientists d) ignoring any experimental evidence that does not fit the theory