For German Military Strategists, the Entry of the United States

For German military strategists, the entry of the United States into the war in April 1917 meant that

A) they would no longer be able to use their submarine weapon effectively.
B) they would have to defeat France and Britain before a large American force arrived in Europe.
C) they would have to seek an immediate cessation of hostilities and peace treaty with Russia.
D) the war would become one of swift movements rather than stalemated trench warfare.
E) they would have to switch from an offensive to a defensive strategy.