Answer:
A. global trade
Step-by-step explanation:
Like the modern bubonic plague, scientists believe the Plague of Justinian spread through fleas. Studies indicate the plague may have originated in China or India and was then transported to the fertile valleys of Egypt through trade routes.
The plague is thought to have originated in Asia over 2,000 years ago and was likely spread by trading ships, though recent research has indicated the pathogen responsible for the Black Death may have existed in Europe as early as 3000 B.C.