Final answer:
The South lost potential support from Europe after the freeing of slaves during the Civil War, as it aligned the Union with anti-slavery sentiments, which conflicted with Europe's stance against slavery.
Step-by-step explanation:
The South was significantly impacted by the freeing of the slaves during the Civil War in multiple ways, but regarding the options provided, a) It cost the South the support of Europe is the most accurate. The Emancipation Proclamation issued by President Lincoln not only declared the freedom of slaves in Confederate-held territory but also altered the nature of the war to a fight against slavery. This positioned the Union on moral high ground, making it diplomatically problematic for anti-slavery European nations, particularly the United Kingdom which had made efforts to suppress the slave trade, to support the Confederacy. This eroded the potential for European intervention on behalf of the South, which could have had significant implications for the outcome of the war.