Why Are There Never More Than Two to Three Levels

Why are there never more than two to three levels of carnivores in the trophic pyramid of an ecosystem?

A) Carnivores take up a lot of space.
B) Most of the energy in each trophic level is used up before it is passed to the next level so after two to three levels above the herbivores, it's gone.
C) There aren't enough herbivores to support them.
D) The carnivores are very inefficient in their use of energy, so it gets lost.
E) Humans hunt the carnivores.