The German U-boats blocked British Isle and attacked merchant ships affecting the trading business of US with British, but at some stage the U-boats started to attack ships taking the lives of unarmed passengers, as with the Lusitania ship, which 120 American died. The Germans were asked to stop the attacks but they did not and many US ships sank, shedding off US citizens lives. The submarine warfare enraged the US neutrality which then turned against the German and declared war on March 1 in 1917.
The Founding Fathers tried to create republicanism, when they divided powers between the judicial, legislative and executive branches. The correct option among all the options that are given in the question is the first option. Checks and balances is also very close to being the answer to this question.
By defeating inavaders and crushing internal opposition
