The Interactions Between the American Chestnut and the Parasitic Fungus

The interactions between the American chestnut and the parasitic fungus Cryphonectria parasitica best exemplify the principle that

A) parasites can drive host populations to extinction.
B) parasites can influence host population cycles.
C) selection can favor a diversity of host and parasite genotypes.
D) vaccination can reduce the incidence of disease.