A.Why American industries grew rapidly in the nineteenth century.
B.How advances in transportation helped American cities develop.
C.Transportation between the cities of the United States.
D.Great American inventors of the nineteenth century.
A.It was no longer possible to keep horses.
B.It was difficult to find jobs.
C.They could no longer walk to work.
D.They had to pay more for their housing.
A.They could be controlled independently.
B.They were fire resistant.
C.They could keep operating for a longer period of time.
D.They offered more room for passengers.