D. It allows citizens of many European countries to freely travel across the continent.
Expansion of Slavery impacted the lives of already enslaved people, by causing them to continue being abused and held as slaves. The expansion further strengthened the practice of slavery, making it even harder for slaves to escape and causing more people to be enslaved too.
The main impact of the invention of the cotton gin in 1793 was on the ability to process short-staple cotton.
