Why Is Yersinia Pestis, the Causative Agent of Bubonic Plague

Why is Yersinia pestis, the causative agent of bubonic plague, considered a potential biowarfare agent?

A) The bacteria is readily available in Europe.
B) There is no effective antibiotic against it.
C) It is readily introduced into the human population by mosquitoes.
D) Pneumonic plague is highly communicable with a high mortality rate.
E) The bacterium forms long-lasting endospores.