I believe c is the answer because the word it's is saying it is
It would be mainly that "<span>D. More than one person wishes to control the same piece of land" that generally </span>has been the main cause of land grant disputes over time, since land is of course limited and very valuable.
The <span>policy of Europe that helped spark U.S. expansion overseas is Imperialism. Imperialism is, by definition, the expansion of a nation in other countries in order to exploit the country's resources and people. Imperialism helped the U.S. expansion because of their goods and services that were sold in Europe.</span>