American expansion abroad was fueled by all of the following except

a. the closing of the frontier
b. a rise in industrial production
c. fear of being closed out of asian markets
d. economic prosperity in the early 1890s

which was an important result of the spanish-american war?

a. the philippine islands gained their independence.
b. the united states became an imperial power.
c. the battleship "maine" was blown up.
d. the united states supported the sovereign rights of the cuban people.