During Spring 1918,the War Changed Momentum on the Western Front

During spring 1918,the war changed momentum on the Western Front due to several factors,the most important of which was:

A) an increase in the morale of Allied front-line troops.
B) new tactics,which were first used by the French.
C) the Allies' material advantage finally coming to bear on the Germans.
D) the arrival of fresh American troops at the front in the region of the Somme.
E) the near collapse of the German army after a failed attack along the entire front.