3. how did william howard taft try to change the open-door policy in china?

Answer:

William Howard Taft tried to follow few steps to change the "Open-Door policy" in China.  The main motive of “Open Door policy” was to open trade with the Chinese markets. The policy was supported by all the rivals as well as this guaranteed that the geographical and constitutional integrity of China will remain unchanged.

In East Asia, “Dollar diplomacy” was introduced by William Howard Taft. He decided to use the economic strength of America to establish a strong American involvement in China. This would promote U.S. trade and investment in China. It basically aimed to minimize the use of military threat and use America’s bankers and industrialists to invest in new opportunities outside America.