Respuesta :
c.submarines
why?
Germany broke its promise to the United States to stop attacking passenger ships (unrestricted submarine warfare). German leaders knew America entering the war would increase the strength of Allied Powers.
I would say Submarines because of the sinking of the Lusitania. Nuclear warfare was not in WWI, machine guns had nothing to do with the U.S. and they have been using poisonous gas since the beginning, so submarines would be the answer. I hope that was helpful.
