which of the following statement(s) are true about the atoms of any element? a. the number of protons in an atom of an element is unique to each element b. the number of protons and neutrons in ana atom of an element is unique to each element c. a proton is an atom of one element that is identical to a proton in an atom of another element d. the number of protons in an atom of an element is the same for all elements