Concept:Energy conservation is needed to balance energy supply and demand and to reduce environmental pollution.Explanation:Insufficient production of energy means available supply cannot meet all needs, so saving energy becomes necessary.Increasing demand of energy puts pressure on existing resources, making conservation important.Limiting production of carbon(IV) oxide is also a reason because using less energy reduces burning of fuels, which cuts CO2 emissions.Therefore, all three statements I, II and III are valid reasons for conserving energy.Answer:D. I, II and III