Technologicalimprovements and reduced equipment costs have made converting solar energydirectly into electricity far more cost-efficient in the last decade. However, the threshold of economic viabilityfor solar power (that is, the price per barrel to which oil would have to risein order for new solar power plants to be more economical than new oil-firedpower plants) is unchanged at thirty-five dollars. Which of thefollowing, if true, does most to help explain why the increased cost-efficiencyof solar power has not decreased its threshold of economic viability? A. The cost of oilhas fallen dramatically. B. The reduction inthe cost of solar-power equipment has occurred despite increased raw materialcosts for that equipment. C. Technologicalchanges have increased the efficiency of oil-fired power plants. D. Most electricityis generated by coal-fired or nuclear, rather than oil-fired, power plants. E. When the price of oilincreases, reserves of oil not previously worth exploiting become economicallyviable.