Answer:
C. Ecological Succession.
Step-by-step explanation:
A is incorrect because predation is the act of an animal preying on another animal for food which has nothing to do with grass and trees. B is incorrect because saprophytism is the ability of certain plants to live in dead or decaying organic matter. For example, imagine mushrooms growing on decaying trees. That still doesn't explain what the REPLACEMENT of grasses, bushes, and trees are called. D is incorrect because that is energy transferring to another, that answer wouldn't make sense. From what I know, ecological succession is the process of change in the species structure of an ecological community over time. So, if there is an abandoned field but grasses and trees are slowly popping up there over time (There's a lot more to it) then C, ecological succession is your answer.
Hope this helps! :3