Water, air, food. and heat.
The answer is A. This ensures that the resource has enough time to regenerate so as to sustain consumption. An example is that of the carrying capacity of a habitat. If a herd of cows exceed the carrying capacity of the grazeland, the grass will be depleted and the area will be predisposed to desertification. The environment will not be able to sustain the cows anymore until the herd number reduce.
