Technological improvements and reduced equipment costs have made converting solar
Which of the following, if true, does most to help explain why the increased cost-efficiency of solar power has not decreased its threshold of economic viability?
A. The cost of oil has fallen dramatically.
B. The reduction in the cost of solar-power equipment has occurred despite increased raw material costs for that equipment.
C. Technological changes have increased the efficiency of oil-fired power plants.
D. Most electricity is generated by coal-fired or nuclear, rather than oil-fired, power plants.
E. When the price of oil increases, reserves of oil not previously worth exploiting become economically viable.
(2)：火力发电的成本=石油的成本+将石油转化为电能的成本 这两个公式的区别在于：太阳能是不要钱的，而石油要钱。 而当石油的成本=临界点(threshold)的时候， (1) = (2) 即：太阳能转化成电能的成本= threshold+将石油转化成电能的成本 由此得到：(3) threshold= 太阳能转化成电能的成本 - 将石油转化成电能的成本 所以，threshold只是两种发电成本的差，是由两种发电的成本决定的，与实际的油价并没有关系。所以，A选项是无关选项。 而题目中提到说，太阳能转化的效率提高（即成本下降），而threshold不变，那么从公式(3)中就很容易得到：是因为石油转化成电能的成本也降低了（即火力发电效率提高）。 所以选C。
- Many Runagian senior citizens are no better off financially now than they were before the increase.The phrase “better off” is closest in meaning to________?
- The word "accidental" is closest in meaning to___________ ?
- Who can it be? I’ m quite ____ a loss to guess．
- The number of people flying first class on domestic flights rose sharply in 1990, doubling the increase of the previous year.
- The word "conspicuous" is closest in meaning to______ ?