Final answer:
Option (A), Guam, Midway, and Samoa functioned as naval bases and refueling stations, supporting American military and merchant vessels, and were essential to the United States' strategic interests during periods of expansion and conflict.
Step-by-step explanation:
The function of Guam, Midway, Samoa during their peaks of strategic importance was as naval bases and refueling stations. These locations served as critical resupply points for both merchant vessels and naval ships, facilitating American expansion and global reach.
For example, the naval refueling station at Pago Pago in Samoa was essential for American ships. During World War II, stations like Guam became key military posts. Meanwhile, the Midway Islands offered a more stable path to Asian markets and served as a vital naval coaling station, key for steamship operation across the Pacific.