The demand on the earth's lithosphere is dramatically increasing. why should we look for alternative sources of energy other than just relying on fossil fuels? a) fossil fuels are non-renewable and exhaustible and their combustion causes air pollution. b) fossil fuels are renewable and plentiful, but their combustion causes air pollution. c) fossil fuels are plentiful, so alternative sources are not needed. d) fossil fuels are not profitable for energy companies.