What was the purpose of the open door policy? a. to provide the united states with access to trade with china b. to make sure that the united states would be open to all world nations c. to provide china with access to trade with the united states d. to make sure that all world ports would be open to the united states

 a. to provide the United States with access to trade with China.

The Open Door policy was issued by the United States in 1899-1900 as a series of dispatches from the US Secretary of State to other nations that had trading interests in China --  Great Britain, Germany, France, Italy, Japan, and Russia.  The policy reasserted earlier agreements that all countries should have equal access to ports in China, with no favored "spheres of influence" for one nation or another.  The United States was seeking to maintain an equal footing with other nations in the access to trade in China.  

d. she conquered the black sea coast and parts of poland.