The carrying capacity for a species in an ecosystem is primarily determined by a. the species’ fertility b. the number of predators c. the ecosystem’s resources d. a boom-and-bust curve

  C; the ecosystem’s resources

Explanation: The carrying capacity of a biological species is the maximum number of individuals that a given environment can sustain indefinitely.

This number depends on the disponibility of things like the necessities of the species, like water, food, habitat and other things. Those things are the resources of the environment/ecosystem.

Then the correct answer is option C; the ecosystem’s resources

as the gila monster consumes the eggs or young of the desert cottontail and gambel's quail, thus its main food supply is only accessible for a restricted time duration every year. however, for this, the gila monsters exhibit three adaptations, which elevate their survival rate in the desert condition.  

first, is that they possess huge bodies, and can consume greater concentrations of food during a small period. secondly, they require to feed infrequently as they can accumulate fat in their tails. ultimately, their rate of metabolism is very low, so that they can burn their reservoirs of fat gradually.