The correct option is A sere
Succession is a sequence of events in changing the structure and species composition of a physical environment. In this process, at a particular stage, a particular species predominates, this is known as a sere. With the passage of time, the resources availale in the physical environment change the species composition. The successive colonization of a site by certain species is accompanied by the extinction of other.
Strata is used in case of stratification which is vertical zonation or layering of a community.
Trophic level is used for the flow of energy in a food chain.