Although hydroelectricity is the least expensive energy source used to generate electricity, most utility companies in the United States do not use this form of energy because–


A
hydroelectric plants tend to last longer than plants powered by fossil fuels.


B
hydroelectricity causes more pollution due to the emission of greenhouse gases.


C
hydroelectric plants are expensive to construct and need expensive machinery.


D
reservoirs associated with dams can be used for irrigation as well as recreation.