Final answer:
The Open Door Policy helped prevent the division of China by European colonies and maintained China's territorial integrity, while offering equal access to trade for all nations, which, in reality, favored the US as it produced higher quality and cheaper goods.
Step-by-step explanation:
The Open Door Policy fundamentally affected China in the long run by C. preventing European nations from carving China into separate colonies. It was a diplomatic effort by the United States, through Secretary of State John Hay's Open Door Notes, to preserve China's territorial and administrative integrity while ensuring all nations had equal access to Chinese trade.
The policy's main focus was to prevent the major powers from restricting trade by other nations within their spheres of influence, to allow for free trade across China's ports, and to avoid the colonization and division of China. It aligned with the United States' interests, as it sought to protect and expand upon its own trade opportunities within China without resorting to imperialism or military actions.