In Nature,animals Tend to Be Either an Opportunistic or Equilibrium

In nature,animals tend to be either an opportunistic or equilibrium species or somewhere along an intermediate point between the two.Why aren't there animals in nature that are both big,fierce,and highly reproductive so they leave many offspring?

A) Most animals are both opportunistic and equilibrium species.
B) There is no limitation; such an animal could evolve.
C) It is structurally impossible for a large animal to have many young.
D) You can "spend" your energy to be a large equilibrium species,to produce many offspring as an opportunistic species,or to be somewhere in between,but you can't spend the energy to be both large and highly reproductive.
E) Large animals are incapable of producing large numbers of offspring.