One of the Discoveries Labor Historians Have Made Regarding American

One of the discoveries labor historians have made regarding American workers' social mobility is that

A) skilled laborers rose rapidly while unskilled laborers almost never did.
B) the greatest opportunities for workers were on the American frontier.
C) ingenuity and inventiveness were more important than wage rates.
D) different ethnic groups defined success in different ways.
E) European immigrant workers were content with lower status.