Answer:
A.
Explanation:
President Abraham Lincoln, in 1863, issued Emancipation Proclamation as a necessary action of freeing the slaves in Confederate States.
On January 1, 1863, President Lincoln issued the Proclamation to Confederate States to set free the slaves or else they will be freed using army force. This Presidential Power was used by President Lincoln as a Commander in Chief.
He used this power which is stated in Article 2, Section 2, of the US Constitution. According to this article, a President can use the power as a Commander in Chief 'when the nation calls for it.'
Thus the correct answer is option A.