I would say characteristics because that's how is organized in the animal kingdom
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.
The answer is the second choice
The answer is D) Stationary
(Not a 100% on this but, I'm like 90)