According to the reading, how did the bubonic plague first spread among countries?

Since you didn't provide the text, i can tell you that it first spread from Asia to Italy using merchant ships through rodents. Rodents who were infested would infest people and other animals, more so fleas, who would carry it over to humans, who would then carry it over to other humans, etc etc.

Ibelieve the answer is d

Can u explain more plz