The correct option is C.
In a newly emerged ecosystem, the stages of the ecosystem development is often divided into three basic stages, which are pioneer, intermediate and climax stage. The intermediate stage of the ecosystem development is also called seral stage and the seral community refers to the community of plants that occupy the ecosystem during the intermediate stage. From the information given in the question above, it can be seen that annual weeds and shrubs occupied the ecosystem during the intermediate stage.
