Answer:
The answer would be C.
Explanation:
This is because Abraham Lincoln's Gettysburg Address became very well known. The emancipation proclamation was saying that Lincoln would free the slaves. The last choice was also something Lincoln did that had a big impact because this is were the former slaves were going to be able to be free.
Slavery was not as prevalent in the North as it was in the South due to economic and geographic factors.
The key factor was the type of economy in the North versus the South.
Very quickly, the Northern economy became based on industry while the Southern economy was largely based on large scale plantation style farms.
The end result was that the South needed slaves more for their type of economy to be profitable.