The reason many people most likely attacked the emancipation proclamation was because explain as well

a)
allowed some states to continue to use slave labor.

b)
opposed the thirteenth amendment to the constitution.

c)
stated that freed slaves could join the u. s. military.

d)
prompted foreign countries to support the confederacy

The answer is A) allowed some states to continue to use slave labor.

Why is it A)? because many people attacked the Emancipation Proclamation because it allowed some states to continue to use slave labor. Border states such as Maryland and Delaware, which had remained loyal to the Union, were allowed to continue using slave labor, as were any states already under Union control.