Final answer:
The bubonic plague spread through rats and the movement of people on trade routes and long distances.
Step-by-step explanation:
The bubonic plague, also known as the Black Death, spread through various means of transportation and movement. It was primarily spread by rats that carried fleas infected with the Yersinia pestis bacterium. These rats traveled on trade caravans and merchant ships, allowing the plague to spread along international shipping and trade routes, such as the Silk Roads and the Mediterranean Sea.
Additionally, the movement of people played a significant role in the spread of the plague. The Mongol armies unintentionally brought infected rodents among their foodstuffs as they traveled long distances. The Mongols' protection of merchants and long-distance travelers during the Pax Mongolica further facilitated the spread of the disease. Finally, those forced to leave their homes due to famine and environmental changes created another pathway for the plague to spread.
In conclusion, the transportation and movement of rats, as well as the movement of people, played a crucial role in the spread of the Bubonic Plague.