What primarely determines the carrying capacity of a population

Amount of resources within the region of that population

Explanation:

Correct Biotic and abiotic limitations

Carrying capacity is defined as the total number of an organism who can be supported in a given area within the natural resources limit and without harming or degrading the natural, economic or the cultural environment present for the future generations.

Carrying capacity is determined by the limiting factors, which are known to affect the natural resources available. It may include water, nutrients, minerals, space, light etc.

explanation:

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.