All elements are pure substances.
Renewable energy has the potential to have all the same applications as non-renewable. But we currently don't have the resources and potential.
So I would say the answer would be B, but this question is somewhat confusing.
CH4 + 2O2 =======> CO2 + 2H2O
Properties change within a Row (or period) as the number of valence electrons in the outer shell increase
