The passage implies that the full impact of the railroads might be easily seen in ______.

A．Other modes of transportation did not come to an end when the first train appeared.
B．There was little government subsidy.
C．People doubted that railroads stretching desert, mountain, and semiarid plain could be profitable.
D．Economists and congressmen strongly opposed the idea of linking the East and West together through railroads.

A．The impact of railroads was still limited.
B．Passengers and freight had to transfer from railroads to other modes of transportation to reach western destinations.
C．Wagon freighters continued operating.
D．Railroad travel was quite expensiv