问答题 翻译：The most widely used indicator of a crude oil's worth to the producer is its API (American Petroleum Institute) gravity.

问答题 翻译：The operation of a gas transmission system that moves gas over a large geographic area and contains several compressor stations and other facilities is a complex control challenge.

问答题 翻译：The success of nontechnical methods averages 4.4% or about one third as success as technical methods.