After the entry of the united states into the war germany decided its only hope for victory was to ?

Break through in the west before American troops arrived.

Explanation:

Although resistance to the war had been high in the United States, the country joined World War I in 1917. The first American troops arrived in France on June 25, and they were known as the American Expeditionary Force. The arrival of the troops led to a boost in morale among the Allies. It also made winning more difficult for Germany. Worried about the state of the war, the Germans decided to break through in the west before the American troops arrived.

i would say your answer would be the second option.

hope this !