What Was the Purpose of the Open Door Policy

What was the purpose of the Open Door policy?

A) It allowed a certain number of Japanese immigrants into the United States in exchange for trading rights.
B) It allowed Cubans to enter the United States and Americans to enter Cuba freely to benefit the economy.
C) It proposed that foreign powers keep China trade open to all European and American nations on an equal basis.
D) It pledged aid to struggling Latin American republics out of solidarity with the United States' "next door" neighbors.
E) It closed Chinese immigration except for spouses and children of men already in the United States.