Answer:
Option (D) is correct.
Step-by-step explanation:
According to the Rutherford's atom model, almost entire mass of the atoms consists in the small central core. This small central core is called the nucleus of the atom.
Nucleus contains protons and neutrons.
Mass of one proton is 1.67 x 10^-27 Kg
Mass of one neutron is almost same as that of mass of one proton.
Mass of an electron is 9.1 x 10^-31 Kg.
Mass of electron is much lesser than the mass of proton and neutron, so almost entire mass of the atom consists in the nucleus.