American expansion abroad was fueled by all of the following EXCEPT

Athe closing of the frontier
Ba rise in industrial production
Cfear of being closed out of Asian markets
Deconomic prosperity in the early 1890s

Which was an important result of the Spanish-American War?

AThe Philippine Islands gained their independence.
BThe United States became an imperial power.
CThe battleship "Maine" was blown up.
DThe United States supported the sovereign rights of the Cuban people.