The past is always tense, the future perfect.
你们必须掌握许多知识,让它们在你们的头脑里形成一个思维框架,在随后的日子里能自动地运用它们。
法律体系是根据其自身的有效性标准而有效的规则体系。
The future of the petroleum industry lies in efficiency, cleanliness, and low carbon. We must find a balance between traditional and new energy sources.