Answer:
The right answer is:
A.It shifted the purpose of the war from preserving the Union to freeing the slaves.
Step-by-step explanation:
Freeing slaves became a legitimate war objective after the Emancipation Proclamation of January 1, 1863. It was made possible only because of LincolnĀ“s firm commitment to issuing the document and after the Battle of Antietam that allowed the Union to expel the Confederates from Maryland, an event seen as a "victory."