While all the options you provided relate to factors that contributed to American imperialism in the late 19th century, the most strategic factor besides the need for raw materials would likely be B: the need for more naval bases to protect economic interests.
During this period, the United States sought to expand its influence and secure trade routes, which was underscored by Alfred Thayer Mahan's advocacy for a powerful navy and coaling stations abroad. Establishing naval bases was seen as essential to protect American economic interests, facilitate trade with Asia and other regions, and support military operations if necessary. This strategic focus on naval power was a significant driver of American expansionism during the late 19th century.