What Once Was an Open Pasture on a Long Abandoned

Multiple Choice

What once was an open pasture on a long abandoned farm has changed over time,without the direct influence of humans.After the cattle had been removed,shrubs and bushes could be seen dotting the grass-covered hillsides.A few years later,small pine trees and then larger deciduous trees appeared.Now,there are so many trees and shaded regions it is difficult to tell that this was once a field.
-In this wooded region that was once pasture,a mature forest of towering oaks and hickory trees has taken over.However,change is still apparent,as a large patch of young shrubs and small trees are growing where several large trees were toppled by a storm several years ago.Collectively,this wooded region represents

A) a climax ecosystem.
B) primary succession.
C) a sustained biome.
D) intermediate succession.