Answer:
Option C.
Step-by-step explanation:
Germany was sinking American ships, is the right answer.
The most important reason for the entry of the United States in the First World War was that Germany was sinking American ships. Woodrow Wilson, the then U.S. President mentioned Germany's breach of its commitment to cease permitted submarine combat in the North Atlantic and the Mediterranean, and its attempts to lure Mexico into engagement against the U.S. as his intentions for protesting the war.
The U.S. entered the war because of the Germans' decision to maintain the course of unlimited submarine warfare and at the time when Germany seized two of the American ships, America announced to enter the war.