Answer:
Professor Margaret MacMillan discussed the evolution of public opinion in the United States during World War I and its eventual decision to enter the war in 1917Explanation:
This Presidents and the Constitution e-lesson focuses on Abraham Lincoln and the Emancipation Proclamation. Though he had always hated slavery, President Lincoln did not believe the Constitution gave him the authority to bring it to an end-until it became necessary to free the slaves in order to save the Union. With the Emancipation Proclamation, which he viewed as an essential wartime measure to cripple the Confederacy’s ability to fight, Lincoln took the first step toward abolition of slavery in the United States.
The answer is Indentured servants.