Answer:
B.Aggressive behavior leads to fights that allow stronger animals to kill off weaker members of the species.
Step-by-step explanation:
Take a wolf pack as an example; to figure out who the alpha is after the old one dies the beta will temporally take post as alpha. If another wolf of the pack can beat the alpha(not to death just til surrender) then the beta will stand down as alpha and the winner will be alpha. One wolf pack will also attack other wolf packs if that pack feels as though their territory line has been crossed or if the trespassing pack attacks a pup. In some but very few cases an alpha will lose there place in the pack if another member of the pack does the "alpha's job" better without violence; most of the time when that happens the two wolves will still fight if the og alpha feels its necessary.