Question

In The Significance of the Frontier in American History, Frederick Jackson Turner wrote:

"The frontier has gone, and with its going has closed the first period of American history."

Source: http://xroads.virginia.edu/~hyper/turner

How did advocates of expansionism react to Turner's frontier thesis?

A.They argued Americans should move from rural areas to expand the nation's new frontier—the cities.
B.They argued Congress should enact new protections for America's natural resources to rebuild the frontier.
C.They argued Americans should seek new lands overseas as a "safety valve" to help release popular discontent.
D.They argued Americans should turn away from the culture of the American West and embrace European culture.