Americans wanted to move west primarily for C: land ownership. The promise of owning land, especially during the period of westward expansion in the 19th century, motivated many settlers to seek new opportunities. Factors such as the Homestead Act, which provided land at little or no cost, and the desire for farming and economic independence drove many individuals and families to move westward. While the open plains (A) did offer land, the overarching motivation was the desire for ownership and the opportunities that land could provide.
Shipping routes (B) and large cities (D) were not primary motivations for westward expansion in the same way that land ownership was. Instead, people were often seeking to escape crowded urban areas.