Theoretically, living organisms are capable of producing populations of infinite size. however, this never occurs because population sizes are limited by

Its all of these.

Explanation:

Even though living organisms are capable of producing populations of infinite size, they are ultimately limited by

organism interactions and behaviors (e.g., cooperation, competition, etc.)

the availability of resources, such as food, water, and shelter

environmental conditions, which, in turn, may be affected by natural causes (e.g., tornado, fire, flood) or human causes (e.g., pollution, deforestation)