Diction E.g.1 Although all petroleum is composed essentially of a number of hydrocarbons,they are present in varying proportions in each deposit and the properties of each deposit have to be evaluated. 虽然石油主要由各种碳氢化合物组成，但 是这些碳氢化合物以不同的比例存在于 各种矿床中，因此必须对各矿床的特点 做出评价。 Chapter 4 AdequacyDiction E.g.1 Although all petroleum is composed essentially of a number of hydrocarbons, they are present in varying proportions in each deposit and the properties of each deposit have to be evaluated. 虽然石油主要由各种碳氢化合物组成，但 是这些碳氢化合物以不同的比例存在于 各种矿床中，因此必须对各矿床的特点 做出评价。 Chapter 4 Adequacy