Answer:
(4) adoption of the 13th amendment to the Constitution
Explanation:
The Thirteenth Amendment to the United States Constitution ('Amendment XIII') officially abolished and continues to prohibit slavery in the United States of America, and, with limited exceptions (such as those condemned for a crime) prohibited involuntary servitude.
At the time of ratification, slavery remained legal only in Delaware, Kentucky, Missouri, Maryland and New Jersey. In the rest of the United States the slaves had been freed by the state action and the "Emancipation Proclamation" of the federal government.
Abraham Lincoln (who had promulgated the Proclamation) and others were concerned that the Proclamation of Emancipation would be seen as a temporary measure only during the American Civil War, and, therefore, in addition to the liberation of slaves in those states where slavery It was still legal, they supported the Amendment as a means of guaranteeing the permanent abolition of slavery.