B. A reason to move to a place
In the eighteenth century, the handling of cotton was very laborious, so it was necessary to manually separate the seeds and fabrics, which affected productivity.
Then, in 1793 Eli Whitney built a device that separates cotton seeds from cotton fiber, called cotton gin. This invention quickly became a necessity because it allowed the cotton to be produced in higher quantities and at a cheaper price, boosting the cotton industry.
Depending on your theory.
In my opinion, it did.
The failure of the Treaty at Versailles (created after the end of WW1) caused WW2.
The Communist party and Soviet Russia, because they claimed to be the "saviors" of the working class.They insistence had been exploited by the rich and elite who didn't work.