The action that broke off the negotiations between Japan and the United States was b. Japan’s invasion of Indochina.
The Japanese kept wanting to expand in WWII and to this effect, invaded Indochina which was under the control of the French.
This was an escalation of the war to the United States, and they decided that Japan did not want peace. The negotiations between both nations subsequently broke down.
In conclusion, option B is correct.
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