Final answer:
The 'Open Door Policy' started by the United States in China aimed to promote open trade and prevent colonization. The United States and its allies initiated open trade with China.
Step-by-step explanation:
The 'Open Door Policy' started by the United States in China in 1899 aimed to promote open trade and prevent the colonization of China by foreign powers. Option B, 'The United States and its allies started open trade with China,' accurately describes the policy. The United States wanted equal access to China's markets for all countries, rather than China being dominated by a single power.
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