During the Civil War, Practicing Effective Diplomacy for the Union

During the Civil War, practicing effective diplomacy for the Union and the Confederacy in their respective relations with Great Britain

A) played only a small role in the evolution of the war efforts of the Union and the Confederacy.
B) was important for the Union but not for the Confederacy.
C) was critical for both the Union and the Confederacy
D) was important for the Confederacy but not for the Union.
E) was completely irrelevant to the outcome of the Civil War.