单项选择题
A．harnessing energy through chemistry B．our last source of power C．how water power is produced D．the amount of solar energy that can be utilized
A．Even windmill' s action depends on the sun. B．The sun produces enormous energy for man to make use of. C．Some day man will be able to utilize 100 % of the solar energy that gets to the earth. D．The sun produces different heating effects in different places.
A．100 % but indirectly B．5 % C．50 % D．only a very tiny amount