Compared with the Efficiency of a Typical Steam- Electric Generating

Compared with the efficiency of a typical steam- electric generating plant, the efficiency of a typical hydro- electric generating plant is

A) smaller, because only a small amount of the energy in the water behind a dam can be converted into electricity.
B) about the same, because both are heat engines and so both have the large inefficiency implied by the second law of thermodynamics.
C) greater because a hydro- electric plant is not a heat engine and so it does not have the large inefficiency implied by the second law of thermodynamics.
D) smaller because a steam- electric converts thermal energy into non- thermal forms and the second law of thermodynamics implies that this is a highly efficient process.
E) greater because a hydro- electric plant uses the sun as its source of energy, rather than hard- to- obtain fossil fuels.