I believe it was the use of poisonous gasses, which they not only used on the Jews but in war too......., or The newly created Machine gun<span />
The Depression of 1920-1921 resulted in a sharp increase in the tariff rates. The correct option among all the options that are given in the question is the last option or the fourth option. It was a big deflationary recession that happened in the United States of America. I hope the answer has helped you.
The North Atlantic Treaty Organization was created in 1949 by the United States, Canada, and several Western European nations to provide collective security against the Soviet Union. NATO was the first peacetime military alliance the United States entered into outside of the Western Hemisphere.
A. Corporate and government excesses.
Muckrakers attacked institutions and leaders to make them seem as though they were corrupt.
Hope this helps :)<span />