Final answer:
The Open Door Policy of America required foreign countries to give up their economic control in China for it to succeed.
Step-by-step explanation:
In order for the Open Door Policy of America to succeed, the assumption that had to be true is that other foreign countries would have to give up their sphere of economic control in China. The Open Door Policy was a diplomatic initiative that aimed to ensure equal trading opportunities for all countries in China. By giving up their exclusive economic control, foreign nations would allow for fair competition and economic independence for China.
For example, under the Open Door Policy, the United States advocated for an end to the spheres of influence where foreign powers controlled specific regions in China. This would allow for a more open and inclusive trading environment.
It is important to note that the other assumptions mentioned in the options could also be relevant in the context of promoting equality, freedom, and independence, but the primary assumption for the success of the Open Door Policy is the giving up of economic control by other foreign countries in China.
Learn more about Open Door Policy of America towards China