Historians state that the United States' entry into World War I resulted in which of the following outcomes?

Question

A.
It broke the stalemate that had existed for years prior.
B.
It created a second front that required more German soldiers.
C.
It resulted in the introduction of trench warfare.
D.
It led to the widespread use of mustard gas.

Answer 1

A. It broke the stalemate that had existed for years prior.