the lack of new factory jobs in the North" was not an economic problem facing the United States at the end of the Civil War. The others were all quite serious problems.
The factor that had the most influence in the transition from wandering tribes to the emergence of cities would be "<span>a. food," since it was a surplus of agriculture that allowed people to develop trades other than farming. </span>
A. Spanish conquistadors bring their horses with them across the Atlantic. Some horses escape or swim to shore after a ship sinks. The Plains Indians become expert horsemen and buffalo hunters.
This was certainly not intentional since hardly the conquistadors would want their enemies to be stronger.
B. B. Rats are aboard European ships coming to the Americas. The rats spread disease and hunt unknown numbers of smaller animals to extinction.
This is hardly intentional. Rats were almost unavoidable back then and the Europeans just did not care much about them. They weren't thinking about how the rats would cause trouble in the Americas. They were "just rats".
So the only intentional one is:
C. Columbus brought pigs to the Americas on his second voyage. The pigs provided a valuable source of food for a growing population.
Columbus brought pigs for them to serve as food eventually and so they did.
<span>South Carolina declared the 1828 "Tariff of Abominations" was unconstitutional as it imposed extremely high taxes on the southern states for goods that they imported to the northern states. Northern industry was dramatically impacted by the cheap goods made in the South. This is why the South Carolina government voted that the tariff was unenforceable.</span>
