Answer:
Viruses/Virii
Explanation:
Virii(or viruses) can't reproduce on their own. They need to reprogram another cell to make virii.
Invasions by Barbarian tribes
The people that had a nomadic lifestyle meant that they were able to communicate with people of multiple ethnicities, cultures, because they were traveling most of the time and were passing great distances, and they also needed a relatively short amount of time to get from one place to another. Because of this the nomads had knowledge of the technologies in multiple places, so they were the perfect people to spread the new invention. Because of their lifestyle they were also great for trading, and no wonder that the silk road was passing through nomadic lands and was mainly organized by the nomadic people. Unfortunately, besides the positives, there were also negatives in this, like transferring diseases in multiple regions very quickly, like the case with the plague/black death that had devastating effects on the demographics in Asia and Europe.
Answer:
(A)-Most of the industries in the US was centered in the south.
Explanation:
I found this online
