Final answer:
Competition in natural selection occurs because more offspring are produced than can be supported by the limited resources, leading to a struggle for survival where organisms with adaptive traits are more likely to pass on their genes.
Step-by-step explanation:
Competition is central to the theory of natural selection because organisms typically produce more offspring than can be supported by available resources. Competition for limited resources is a direct result of this overproduction, as not all individuals can survive and reproduce given the scarcity of resources such as food, water, and shelter.
Thus, those with inherited characteristics that provide an advantage in the struggle for existence are more likely to survive and pass on those adaptive traits to the next generation. Over time, this process leads to populations that are well-adapted to their environment, a process Darwin called descent with modification.
It is important to note that natural selection is not about the survival of the 'fittest' in terms of strength or dominance, but rather the survival of those that fit best into their environment.
Option A) is the most accurate choice as it reflects the principle observed by Thomas Malthus and later incorporated by Darwin and Wallace into the understanding of natural selection. Intraspecific competition and interspecific competition are both manifestations of the struggle for survival, driving evolution and adaptation within and between species.