your answer is the third one.
Usually representing a solid you used a 3d model.
And there are balls in them representing atoms and in a video it shakes or vibrates to represent the motions of a solid.
Isotopes are variants of a particular chemical element which differ in neutron number (neutral particle)and all isotopes of a given element have the same number of protons (positive particle) in each atom.So isotope B of the sodium will have 11 protons, 11 electrons but it may have a wide range in its number of neutrons.
I believe the answer is D.