The Tripartite Agreement served as a warning to the United States. Option D is correct.
Numerous tripartite agreements have been made between nations such as the Tripartite Agreement of 1940 between Germany, Italy and Japan which created the Axis powers.
Another Tripartite Agreement was the international monetary agreement reached by the United States, France, and Great Britain in September 1936 seeking to stabilize their nations' currencies both at home and in the international exchange markets.