Answer:
B. the Tigris River and the Euphrates River
Explanation:
the region's semiarid climate didn't have much rainfall, with less than ten inches annually. This initially made farming difficult. the Tigris and Euphrates provided a source of water that enabled wide-scale farming.
It was a chain reaction. Long story short, the countries were pulled into the war because of agreements they had with their allies. This treaty is what caused the countries to enter WWI, to protect and defend their allied countries who were already in the war.
The effects of the global trade in silver were worldwide and linked the world in new and unprecedented ways.
