1.There/be/two groups / energy sources :renewable and non-renewable energy sou 2.Renewable energy sources/consist/wind energy/solar energy/hydro energy/nucl 3.They/be/clean/green/not cause pollution. 4.Non-renewable energy sources/include/coal/petrol oil/natural gas. 5.They/be/limited/cause pollution. 6.To conserve fossil fuel,we/use/non-renewable energy sources/as/economically
