Answer:
Umm have you tried quizzlet
Answer:
vaccination
Explanation:
Louis Pasteur had been working to find a vaccine that would cure cholera in chickens. His lab assistant gave an older, weaker strain of the disease to the birds. When these birds did not die Pasteur began to rethink his ideas a came up with our current method of administering vaccinations.
I believe it was Justinian that managed to unite Rome, and expanding the Byzantine Empire.
