What event in 1917 most benefited the Allies?

A. Germany agreed to end unrestricted submarine warfare.
B. Russia signed the Treaty of Brest-Litovsk.
C. Woodrow Wilson published his Fourteen Points.
D. The United States declared war against Germany.

The event in 1917 that most benefited the Allies was the United States declaring war against Germany. Therefore, the correct answer to the question is option D.

The event in 1917 that most benefited the Allies was D. The United States declared war against Germany.