Which is a true statement about the open door policy?
a.the idea for the policy was opposed by the united states.
b.all nations did not want to pay taxes equally.
c.all nations should have equal access to ports of trade.
d.the idea for the policy came from britain and france.

The correct answer is C.All nations should have equal access to ports of trade.

According to the policy, China's trade should be equally accessed by any country that wishes to trade. This was introduced because numerous European powers wanted to make Chinese trading exclusive to them which would make them more powerful  than others. The US came up with the policy to prevent things such as wars.

The answer is b, the Battle of Britain was the RAF (Britian) defending themselves from the Luftwaffe (Germany).