Compared with the Numbers of Grasshoppers or Deer, There Are

Compared with the numbers of grasshoppers or deer, there are not a lot of mountain lions. The reason that large and fierce top-level carnivores are rare in an ecosystem is that

A) such animals do not tolerate other members like them.
B) through natural selection, most fierce animals have been killed off by others.
C) food chains are only 10 to 20% efficient at each step, and top carnivores are therefore limited by the availability of food in their range.
D) only a few such animals are permitted by succession in a biome, and there are only a few biomes.