感谢石油我们有了汽车,感谢石油我们有了飞行的可能
这是倒装句
no one,however,seemed to have realized the importance of this oil until it was found that paraffin oil could be made from it.
但是没有人认识到石油的重要性,直到有人发现可以从石油中中提炼石蜡油
the importance of this oil 所指的this oil明显不是石蜡油,因为后文讲 paraffin oil could be made from it.这里的it就是this oil