The correct answer to this open question is the following.
Although there are no options attached we can say the following.
The Open Door policy attempted to preserve the chances for American businesses to enter which markets?
Answer: in the market of Asia, specifically, in China.
At the end of the 1800s and the beginning of the 1900s, the United States wanted to improve its trade relationships with Asian countries, especially with China. The United States knew that some European nations had some previous trade relations with this country and had some kind of preferences. The United States federal government did not want to be left behind in trade with China, and that is why it formulated the Open Door Policy to close good deals and improve trade with China.