What did the United States mean when it suggested an "Open-Door Policy" in China? All nations were "off-limits" to imperialism in China.
All nations should be allowed to trade freely in all Chinese ports.
All nations should have an exclusive sphere of influence in China.
All nations should pay their respect to the emperor when trade is conducted in China.

The purpose of the Open Door policy was to provide the United States with access to trade with China.

Option A

Explanation:

In order to promote trade with China U.S. proposed Open Door policy in 19th century. This policy essentially professed that trade in China will be open to all the countries equally.

In 1899, John Hay who was U.S. Secretary of State had send the Open Door Note to all the major powers of Europe proposing this policy.  

This policy was professed for avoiding the situation where any one power or country would establish its control over the trade with China. Hence the motive or purpose behind this policy was ensuring that U.S. has access to the trade with China.

Explanation is in the file

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d is the best answer for this question.

c

explanation: