Answer:
D. The Louisiana Purchase.
Explanation:
The idea of Manifest Destiny pushed for the idea that the US was destined to expand westward and to claim lands that make up what is now known as the mainland of the United States of America.
D. The Louisiana Purchase contributed to the idea of Manifest Destiny, as the United States bought France's territorial claim in the New World, which technically meant that the US was free to expand westwards into their legally owned territory.
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