What was the united states'' principal use of guam in the late 19th century and early 20th century?

After the end of the Spanish-American War, Guam became to be administered by the US.

There naval and air bases were established to ensure American checkpoints in the Pacific Ocean, which were very useful in the Pacific Campaign of the Second World War.

With a strategic location in the Pacific, the US Army installations located there are some of the most important in the entire ocean. After the closing of the North American bases in the Philippines, both the Navy and the Air Force Pacific deployments were transferred to this island.

answer; ///i do believe that the correct answer is (b) ///middle colony