Carrying capacity is the ratio of predators to prey the number of populations in a specific area the number of organisms in a population the number of organisms an ecosystem can support

D. the number of organisms an ecosystem can support.

the  carrying capacity   of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available in the environment. thus, it is related to the maximum organisms that can be supported by the resources present in that ecosystem.