The map below shows the location of Guam:

Rectangular map of central Pacific Ocean. Guam and American Samoa are circled and labeled. Inset in map shows region in relation to the Americas and Asia.
Public Domain

What was the United States’ principal use of Guam in the late 19th century and early 20th century?

A. as a location for U.S. owned tropical fruit farms
B. as a source of rubber and oil for U.S. businesses
C. as a prison camp for soldiers captured in the Spanish-American War
D. as a refueling station for U.S. ships traveling to the Philippines