Why was the open door policy advantageous for China?
 a.
 It allowed China to make a trade deal with any country without consequence.
 b.
 It allowed China to deal only with the U.S. at a fraction of the tariff price.
 c.
 It allowed China to let anyone in their country while stopping their citizens from leaving.
 d.
 It created a harmonious relationship between the U.S. and Britain.
 Please answer this as soon as possible I really need this. Please