Final answer:
According to Eric Foner, Lincoln changed his views on ending slavery for three reasons: public opinion, wartime necessity, and political strategy. Hence, the correct answer is option .
Step-by-step explanation:
According to Foner, three reasons why Lincoln changed his views on how to get rid of slavery are C) Public opinion, wartime necessity, and political strategy. Lincoln realized that public opinion was shifting towards ending slavery, and he wanted to align himself with this sentiment to maintain popularity and support.
Additionally, the necessity of emancipation became clear during the war, as slaves working in the South directly aided the Confederate war effort. Lastly, Lincoln recognized the political advantages of incorporating emancipation into the Union cause, as it would deter British recognition of the Confederacy due to their anti-slavery stance.