2. 外语
  3. Petroleum products, such as gasoline, kerosene, home heating oil, residual fuel oil, and lubricating oils, come from one source-

Petroleum products, such as gasoline, kerosene, home heating oil, residual fuel oil, and lubricating oils, come from one source-

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问题     Petroleum products, such as gasoline, kerosene, home heating oil, residual fuel oil, and lubricating oils, come from one source-crude oil found below the earth’s【S1】______, as well as under large bodies of water, from a few hundred feet below the surface to as deep as 25,000 feet into the earth’s【S2】______. Sometimes crude oil is secured by drilling a hole through the earth, but more dry holes are drilled than those producing oils. Pressure at the source or pumping【S3】______crude oil to the surface.
    Crude oil wells flow at varying rate, from ten to thousands of barrel per hour. Petroleum【S4】______are always measured in 42-gallon barrels.
    Petroleum products vary greatly in physical appearance: thin, thick, transparent or opaque, but regardless, their chemical composition is made【S5】______of only two elements: carbon and hydrogen, which form compounds called hydrocarbons. Other chemical elements【S6】______in union with the hydrocarbons are few and reclassified as impurities. Trace elements are also found, but these are of such minute quantities that they are disregarded. The【S7】______of carbon and hydrogen forms many thousands of compounds which are possible because of the various positions and joining of these two atoms in the hydrocarbon molecule.
    The various petroleum products are【S8】______from the crude oil by heating and condensing the vapors. These products are the so called light oils, such as gasoline, kerosene, and distillate oil. The residue remaining after the light oils are distilled is known as【S9】______or residual fuel oil and is used mostly for burning under boilers. Additional complicated refining processes rearrange the chemical structure of the hydrocarbon to produce other products, some of which are used to【S10】______and increase the octane rating of various types of gasoline.
A) degrade B) refined C) up D) light
E) products F) into G) surface H) heavy
I) forces J) combination K) exterior L) found
M) upgrade N) made O) interior
【S6】
选项
答案L
解析 此句的主干为“other chemical elements are few and reclassified as impurities”。由此可见，其他成分为修饰成分，很明显，此处是一个分词结构充当名词的后置定语。符合该结构的只有refined和found，又根据题意，只有found最符合句意。本句意为：人们发现和碳氢化合物混杂在一起的其他化学成分很少，于是把它们重新归类为杂质。
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大学英语四级

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