将简单选择符和组合符结合成链就增加了额外的匹配条件，因此选择符的主题总是那些符合最右端的简单选择符的元素的子集。
Prepending a simple selector and combinator to a chain imposes additional matching constraints, so the subjects of a selector are always a subset of the elements matching the last simple selector.
课程涉及众多主题，包含流程分析、质量管理、供应链设计、以及产品开发。
A wide range of topics are covered, including: process analysis, quality management, supply chain design, procurement, and product development.
主题内容可放在这里。简要介绍主题，并链向其他内容。
Content for subject goes here. Give brief description of subject and link to other content.
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