A. Energy from the sun. B. Natural gas. C. How oil is made. D. Saving energy. 参考答案:A 答案解析:全文紧紧围绕着太阳能这个中心议题,分析了太阳能的优点,如第二段中讲到太阳能取之不尽,用之不竭,能降低空气污染。第三段中谈到使用太阳能时,价格不会像使用其他能源那样,随着那些能源的消耗、减少而价格上涨。
第30题: [单项选择]The term "pour point" is defined as the lowest temperature at which lubricating oils will flow (). A. rapidly B. by gravity C. through a standard orifice at a specified temperature D. at a rate of 60cc per second 参考答案:B