Answer: Enter the world war
Step-by-step explanation:
This was a weird phrasing of the question, so I'll answer as best as I can. True/false doesn't apply here because there are four choice. U-boat attacks on ships during WWI (such as the Lusitania) encouraged war. This brought the US about of isolationism. The League of Nations was formed after WWI, and the US never joined. The spy system answer is irrelevant to me.