What was the most significant use of German submarines during World War I? a. deterring the expansion of the war b. Submarines were supposed to prevent a ground war in Germany. c. preventing the resupply of Allied Forces d. reducing overall casualties

C, submarines were supposed to prevent resupplies of the allied forces, but then an incident happened where a sub shot a neutral ship that killed 200 people & lead the Americans join war, this also lead to the invention of those really fast boats that can detect submarines underwater so that the battleships/supply ships can get to their destination safely