Moseley's changes to the periodic table were based mainly on what part of the scientific process?

observation of the elements< my answer, correct?

argumentation among scientists

existing knowledge about mass

competition among scientists

I think the correct answer would be the first option. Moseley's changes to the periodic table were based mainly on observation of the elements. He works on X-rays involving the elements. He arranged the periodic table  according to the element's protons only disregarding other properties.