What key detail in "Wilson's War Message to Congress" supports his argument for entering the war?

The correct answer for the question that is being presented above is this one: "B. Germany has sunk sea vessels regardless of the vessel’s nationality."

Here are the following choices:

A. The German government acted impulsively by starting the war.

B. Germany has sunk sea vessels regardless of the vessel’s nationality.

C. The people of the United States have sympathy for the Germans.

D. Germany has complete control of many European ports.