Concept:Succession is the orderly, gradual change in the species composition of a community over time.
Explanation:As succession progresses, organisms in the community compete for limited resources such as light, water, space, and nutrients.
Species that are better suited to the changing environment survive and reproduce, while less suited species decline or disappear.
This competitive interaction causes a predictable, directional replacement of species in the community.
Thus, competition is the biological association that directly contributes to the process of succession.
Answer:A. competition