The word "effect" (Line 1, Para. 1) is closest in meaning to" ______ ".

A．increased the money supply in the West
B．was a law passed by state governments in the West
C．made it increasingly possible for settlers to obtain land in West
D．established tariffs in a number of regions

A．built with money that came from the federal government
B．much more expensive to build than they had been previously
C．built predominantly in the western part of the country
D．sometimes built in part by state companies