Were have most immigrants to the united states come from since the late 1900s

C. nudation

Explanation:

When an ecological system has been destroyed by some catastrophe, what is left is usually barren land. This barren land is not suitable for the majority of the organisms to live on it, so changes are needed. Nudation is the first process, and it is part of the primary succession. This process is actually the one responsible for the minor changes that happen on the barren land, preparing it slowly for the organisms to be able to move into it and start developing a new ecosystem.