The black-footed ferret lives on the grasslands of North America. The species is endangered because of habitat loss and disease. What change would cause the species to become extinct?
A. Habitat loss continues to such an extent that the carrying capacity for black-footed ferrets becomes zero.
B. Disease continues to kill a constant percentage of all black-footed ferrets during the first year of life.
C. The black-footed ferret population decreases until the birthrate equals the death rate.
D. The black-footed ferret population decreases low enough for other limiting factors to affect it.