The Emancipation Proclamation affected the Union’s Civil War efforts by increasing the number of troops who could join the Union. Option B is correct.
The Emancipation Proclamation was issued by President Abraham Lincoln on January 1, 1863, as the nation approached its third year of bloody civil war. The proclamation declared "that all persons held as slaves" within the rebellious states "are, and henceforward shall be free."
With the Arms and Space Races becoming increasingly important, Kennedy knew he needed to crush communism as well, to show the Soviets that it was unacceptable for their govt. to spread.