Petroleum
石油
Petroleum has been important since ancient times.
石油自古以来就非常重要，
The Greek historian told of its use in the form of pitch for building and road making.
希腊历史学家表示它的用途是用作修建房屋和道路的沥青。
Petroleum is a fossil fuel.
石油是一种化石燃料。
The liquid comes from the remains of plants and animals that died millions of years ago.These remains were buried deep below levels of rock over time and under great pressure.
它是深埋在岩石层下达数百万年的动植物遗体在重压下经年累月形成的。
This geological process created complex molecules of hydrogen and carbon.
这种漫长的地质作用产生了复杂的碳氢化合物分子。
Oil can also contain other elements.
石油也可以含有其他元素。
Crude oil, or unprocessed petroleum,is called sour when it contains a lot of sulphur, an impurity.
高硫石油是石油刚开采出来为经提炼加工的物质，含丰富的硫。
Sour crude requires more refining than sweet crude,which is low in sulphur and, as a result, often more valuable.
高硫化油比低硫原油需要更多次提炼，因而低硫原油价值更高。
The modern history of oil started in the middle of the 1800s.
石油的现代史开始于19世纪中期，
At that time, a method was found to make kerosene fuel from petroleum.
那时人们已经知道如何从石油中提炼出煤油了。
This kind of fuel became popular for heating and lighting.
这种燃料在取暖和照明上用途广泛。