An atom is represented by
[tex]_z^AX[/tex]
here we know that
z = number of protons which gives an idea of positive charge of atom
A = mass number
it is the sum of number of protons and neutrons of an atom which will help us to calculate the mass of the atom
So here mass number A will give us an idea about the mass of atom
so correct answer will be
A) It contains most of the mass.
