Which development most contributed to the start of the second industrial revolution in the late 1800s?

A synergy between iron and steel, and railroads and coal developed .

Explanation:

It develop at the beginning of the Second Industrial Revolution. Railroads allowed cheap transportation of materials and products, which in turn led to cheap rails to build more roads. Railroads also benefited from cheap coal for their steam locomotives.

here are some events that to cause increased conflict between the north and south

1) mexican cession- gaining modern day california, utah, arizona, and new mexico from mexico. caused southern and northern politicians to fight over whether or not there would be slavery in these newly acquired territories.

2) uncle tom's cabin- this famous book described the cruelty of slavery in the south during the antebellum period, causing more northerners to support abolition and southerners to resent the book as they felt it unfairly depicted southern society.

3) kansas- nebraska act- disagreements over whether or not kansas and nebraska would be free or slave states caused issues between northern and southern politicians in congress.

4) bleeding kansas- this fighting took place in kansas after congress allowed this territory to vote on whether or not they would have slavery. citizens were killed and buildings were destroyed during this fighting.

b or c im pretty sure