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也颇为顾虑，因此这个僵局一直没能打破。中华成语故事这部动画片可以帮助孩子更好的学习成语。As online organizations have broken the time and geographical restrictions, they have saved the time and transportation costs that parents and children have to pay. Secondly, it has the natural advantage of directly facing the national market and allocating the national teacher resources, breaking the regional restrictions on obtaining customers and employing teachers. In addition, in the process of scale-up, online organizations do not need to invest in the training of stores and store managers, so the upfront investment is relatively low.Due to the characteristics of weightlifting:这也是原来那个世界，金庸连载这三部小说的顺序。The Liskov Substitution Principle (LSP) is one of the basic principles of object-oriented design. The Richter substitution principle says that wherever a base class can appear, subclasses can certainly appear. LSP is the cornerstone of inheritance reuse. Only when derivative classes can replace base classes and the functions of software units are not affected can base classes be truly reused, and derivative classes can also add new behaviors to base classes. The Richter substitution principle is a supplement to the "open-close" principle. The key step to realize the "open-close" principle is abstraction. The inheritance relationship between the base class and the subclass is the concrete realization of abstraction, so the Richter substitution principle is the specification of the concrete steps to realize abstraction. --From Baidu