Final answer:
The Open Door Policy was established to protect United States trade in China.
Step-by-step explanation:
The primary reason for the establishment of the Open Door Policy was to protect United States trade in China. The policy was introduced in 1899 by the United States to ensure that all countries had equal access to Chinese markets and trade opportunities. The United States was concerned about the potential exclusion of their trade interests in China by other major powers, such as Britain, Germany, and Japan.
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