A

The main difference between northern and southern slave imports was the fact that first southern slaves arrived with Spanish colonists, whereas the northern slaves were primarily imported by British Empire. Later, when northern states were declaring themselves as free states, there was a flow of slaves to the southern states, which changed southern import of slaves.

Explanation:

The prerequisites of the Civil War were more complicated than the difference in the ideological positions of the North and the South regarding slavery, but the issue of slavery remained one of the most acute. In the North, industry developed rapidly, mainly immigrants worked in production, while the South developed as an agricultural region and mainly slaves worked on its plantations.

Numerous tax and legal issues arose, which became more serious every year. There was a danger that in the framework of one state the northern and southern states of America could no longer exist. The coming to power of Abraham Lincoln after the victory in the elections of 1860 was a signal for the beginning of secession processes.

The southern states began to leave the state, fearing to be in the minority when making landmark decisions at the federal level, although formally the Constitution did not give them this right. As a result, 11 states, which together occupy 40 percent of the territory of the United States, declared their independence.

The next step changing the slave import of the South was the 13th amendment to the US Constitution. It was adopted by Congress on January 31, 1865, ratified by the required number of states on December 6, 1865, and entered into force on December 18, 1865.

This amendment prohibited slavery and forced labor in the United States, except as a sentence of the court as a punishment for crimes. However, the ratification of this amendment was mercilessly delayed. After the victory of the northern states in the Civil War, all the documents mentioned above received real force in the country.