Crosby's focus on smallpox changed his and later historians' views toward ecological and. ... Disease, specifically smallpox and malaria, was the main reason Europeans conquered indigenous peoples. Horses and weapons provided advantages, but infectious disease did the most damage.
Jiaguwen, or Oracle Bone Script
Provided railroad companies land free of charge.
In order to help expand railroads throughout the country after the civil war, congress made railroads expand significantly; bringing even remote parts of the country into a national market economy.
The answer to this question is most likely B or C
