The top number on each of the element tiles represents the atomic mass. Why is that top number different from the atomic number below it?

a.
Electrons and protons make up the mass of an atom while just the electrons determine the atomic number.

b.
Protons and electrons cancel each other out, so the atomic number is smaller than the atomic mass.

c.
Neutrons have no charge, so they are not considered for either number.

d.
Protons and neutrons make up the mass of an atom while the atomic number is determined by just protons.