Which of the following is the best definition of a scientific theory? me plz

Determine the wavelength of the light absorbed when an electron in a hydrogen atom makes a transition from an orbital in the n=3 level to an orbital in the n=7 level.

Darla claims that the first periodic table developed by mendeleev was not completely accurate, so it is not useful at all. harmony argues that it establish the periodic table we use today, making it more credible. who is correct and why? darla is correct, because a model that has any mistakes should be thrown out. darla is correct, because a good model would not need to change. harmony is correct, because mendeleev’s model had all of the information correct in the first version. harmony is correct, because mendeleev’s model made predictions that came true.

How to convert a density of 0.791g/cm3 to lb/ft3