United states and Britain.
C.<em> The President publicly announced slavery would end in southern states</em>. The Emancipation Proclamation was a war measure issued by Abraham Lincoln that freed slaves in Confederate-held lands (excluding non-rebelling states and a few others), with said freedom issuing through advance of union troops or with the slaves running away from captivity.
The measure was created after the mediocre victory of Antietam, with the purpose of changing the reason of the war, from that of preserving the Union to a moral one, of battling slavery. This was crucial for the public and political perception of Lincoln's government (the Union public at least), at the same time helping winning them the war in the front, since roughly 200.000 ex-slave escapees entered the ranks of the Union army.
The answer is B, although C and D could be true they are not mentioned in the passage
That would be the Magna Carta created on June 15th, 1215.
