Final answer:
The Central Powers considered the United States a de facto partner of the Allies due to the significant level of trade and financial support directed towards the Allies, influenced by U.S. isolationism and the British naval blockade during WWI. The correct answer is option: b. they regarded the united states as a partner of the allies.
Step-by-step explanation:
The action the Central Powers took as a result of the United States' foreign policy after the outbreak of WWI was (b) they regarded the United States as a partner of the allies. Initially, the U.S. aimed to maintain an isolationist policy and continued trading with both Allied and Central Powers. However, due to the British blockade, the vast majority of American trade went to the Allies, which included extensive credit extensions. The Central Powers saw this inclination towards the Allies as a partnership by default.
When examining the isolationist tendencies of America as World War II loomed and even after the war began in Europe, it's apparent that the Neutrality Acts were passing through Congress to cement U.S. isolationism. The U.S. shifted from this stance once more as the events overseas escalated, turning from its historical inertia to active engagement, especially after the attacks on Pearl Harbor, which led to a direct U.S. involvement in WWII.