【单选题】People in the United States in the nineth century were haunted by the prospect that unprecedented change in the nation's economy would bring social chaos. In the years following 1820, after severa...
A.
The economic development of the United States in the eighth century.
B.
Ways in which economic development led to social changes in the United States.
C.
Population growth in the western United States.
D.
The increasing availability of industrial jobs for women in the Unites States.