It wouldn't be A because the animals wouldn't really be bothered by each other in the first place. They're not in the same ecosystems.. It wouldn't be D because these animals would be ranked the same if they were in the same phylum. It could be C, but it's not because there is a variety of other resources for them to use. I think B would be the best answer because they are fighting each other for the same resource. You need that resource in order to survive and so does that other organism, so of course both organisms would be fighting over it in order to live
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.