What are the main economic differences between the northern states and the southern states prior to the civil war?

The population of the Northern states was more than twice that of the Southern states. Despite the fact that many people, in both the Northern and Southern states, worked on farms during the time before the Civil War, the Northern become both more industrialized and more urbanized, while plantation agriculture remained the focus in the South.  The industrial transformation which took place in the North caused the two territories’ economies to develop very differently. Transportation improved via railroad development and manufacturing exploded in the North, making it attractive to opportunity seekers looking for improved wages in the North and West states. The cities in the areas offering manufacturing jobs experienced major population growth which triggered extensive housing and urban development, and provided an economic environment conducive to the establishment of a middle-class made up of skilled and white-collar workers.

Idont know which one is right   but i know that c is wrong and a might be wrong

Where are the following