写说明文,是为了“使人有所知”,向读者介绍某一方面的知识。因此,它的主要内容就是介绍事物,解释事理。而要说清一个事物和事理,就一定要抓住该事物的特点和本质。文章的结构顺序要符合事物自身的条理和人们的认识规律,表达方法以说明为主,文中的叙述、描写也要为说明事物服务。《一次大型的泥石流》主要是向人们介绍蒋家 Writing an expository is to “know people” and introduce readers to a certain area of ​​knowledge. Therefore, its main content is to introduce things and explain things. To clarify one thing and affair, one must seize the nature and essence of the thing. The order of the structure of the article must be consistent with the organization of the things themselves and the laws of people’s understanding. The expression method is mainly based on description. The narrative and description in the article should also serve to explain things. “A large-scale mudslide” mainly introduces people to Jiang