Final answer:
The correct answer is option a) Agriculture became the dominant economic activity.
Step-by-step explanation:
Before the Civil War, industrialization significantly changed life in the north but had a lesser impact in the south. The south's economy remained predominantly agrarian, focusing on large agricultural plantations supported by slave labor. Cotton became the major commercial crop, with its production relying on the invention of the cotton gin by Eli Whitney in 1793. While most significant industrial factories were located in the north, the south continued to produce cotton and tobacco for export.
Railroads played an essential role in the expansion of the United States, but the south remained less industrialized and urbanized compared to the north. Therefore, the correct answer to how industrialization changed life in the south before the Civil War is (a) Agriculture became the dominant economic activity.