例题：
　　Passage：…The nineteenth century brought with it a burst of new discoveries and inventions that revolutionized the candle industry and made lighting¹ available to all. In the early-to-mid-nineteenth century, a process was developed to refine tallow (fat from animals) with alkali and sulfuric acid. The result was a product called stearin. Stearin is harder and burns longer than unrefined tallow. This breakthrough meant that it was possible to make tallow candles that would not produce the usual smoke and rancid odor. Stearins were also derived² from palm oils, so vegetable waxes as well as animal fats could be used to make candles…

Which of the following can be inferred from paragraph 1 about candles before the nineteenth century?
a)They did not smoke when they were burned.
b)They produced a pleasant odor as they burned.
c)They were not available to all.
d)They contained sulfuric acid.

　　[解析]
　　正确答案是C。这一段的第一句就告诉我们：19世纪的一些新发明和发现也对蜡烛工业产生了一次巨大的革命，这次革命使得所有的人都使用上了照明。从这句话中我们可以得到两层信息：19世纪蜡烛工业有了一次革命性的变化；在没有这次变革之前，也就是在19世纪以前，照明并不是所有人都能使用的。因为作者在谈论的是蜡烛的变革，所以这里所说的“lighting照明”一定是与蜡烛有关的照明，其实也就是告诉我们19世纪以前并不是所有人都能够使用到蜡烛带来的照明，这一推论出的信息正好与选项C吻合。

　　文章第一句同时也是一个时间的分水岭，告诉我们19世纪蜡烛工业的变革是怎么样的。“在19世纪早期到中期，蜡烛处理工艺使用alkali和sulfuric acid来提炼tallow，提炼后的产品就是stearin，stearin比未经提炼的tallow坚硬而且燃烧得更久。这一巨大的变化意味着制造出不产生烟和rancid味道的蜡烛是可能的。”在这里的一个关键词是rancid，意思是（油脂食物，其味道、气味）不新鲜的；腐臭的；正好与选项b的pleasant odor相反。19世纪前的蜡烛产生usual smoke（经常有烟），这与选项a相反。Sulfuric acid是19世纪用来处理fallow的材料，在19世纪以前是没有使用的，这与选项d相反