问答题 翻译：Classification of traps logically falls into three broad general groups: (1) structural, (2)stratigraphic, and (3)combination.

问答题 翻译：The retort method has several disadvantages as far as commercial work is concerned.

问答题 翻译：Conditions of viscous flow mean that the rate of flow will be sufficiently low to be directly proportinal to the potential gradient.