The correct answer is A. Competition
Step-by-step explanation:
In biology, competition refers to a struggle or fight between different species or organisms to obtain a certain source (water, food, shelter) and therefore survive. Competition is a natural factor that helps to preserved balance in the ecosystem but mainly occurs as the resources are limited, for example, two or more species fed on the same type of plant and there are only a few of these plants available, which led to competition to feed and also influences the surviving rate. Thus, it is competition the one that occurs naturally between organisms in an environment with limited resources.