Question

After the sinking of the Lusitania, the United States responded to an attack on a French passenger ship by doing which of the following?

signing a formal alliance with the Allied powers
issuing the Zimmermann Note and declaring war on Mexico
issuing Germany an ultimatum and accepting the Sussex Pledge
declaring war on Germany and the Central Powers

Answer 1

c the US sent the German gov a series of strongly-worded protest notes, demanding an immediate end to submarine war.

Answer 2

The answer is: issuing Germany an ultimatum and accepting the Sussex Pledge

According to the Sussex flex, Germany agreed to not attacking passenger ships in their sea warfare. Germany violated this agreement two years later because they believe that attacking passenger ships was beneficial to them since it can cut down the supplies from Allied forces.