(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。
- 【OG18-P680-668题】In a review of 2,000 studies of human behavior that date back to the 1940s, two Swiss psychologists, declaring that since most of the studies had failed to control for such variables as social class and family size, none could be taken seriously.
- Following several years of declining advertising sales, the Greenville Times reorganized its advertising sales force two years ago. Before the reorganization, the sales force was organized geographically, with some sales representatives concentrating on city-center businesses and others concentrating on different outlying regions. The reorganization attempted to increase the sales representatives’ knowledge of clients’ businesses by having each sales representative deal with only one type of industry or of retailing. After the reorganization, advertising sales increased.In assessing whether the improvement in advertising sales can properly be attributed to the reorganization, it would be helpful to find out each of the following EXCEPT:
- The author of the passage would most likely agree with which of the following statements about the link between increased solar activity and certain seasonal weather changes on the Earth?
- The passage provides information to support which of the following statement about La Nina?
- Which of the following most accurately describes the organization of the passage?