The correct answer is B) Germany sank the British passenger ship Lusitania.
What caused the United States to enter a war thousands of miles away in Europe was that Germany sank the British passenger ship Lusitania.
United States President Woodrow Wilson had clearly stated that the US would maintain its foreign policy of neutrality to what was happening in Europe. But there were a couple of incidents that made him change his mind. One of them, of course, was the Germans sank the British passenger ship Lusitania. The other incident was the Zimmerman telegram, where the Germans asked Mexico for its help in World War 1. The US intelligence intercepted the telegram. The United States officially entered World War 1 on April 6, 1917.