Answer:
Isolationism
Step-by-step explanation:
I got it right on Edge and the other options are completely wrong.
The US did not appease Europe or Germany when other countries allowed Germany to reclaim some land in a pursuit to stop Germany's aggression.
Blitzkrieg is German for "lightning war" which is a military strategy they used to take countries like Poland
At this time the US had not entered the war so mobilization is therefore wrong.