One of the Reasons That It Is Difficult to Restore

One of the reasons that it is difficult to restore an oak savanna is that

A) Too many weedy species take over the oak saplings
B) There are no natural fires to control vegetation due to human development of the areas
C) Too many trees are cut down illegally for their timber value
D) Too many wild animals destroy the bark of the trees
E) There is not enough suitable land remaining