[总体阅读思考] 读这篇课文,应紧紧把握住以下三个问题: 一、通读全文,理出段落(层次)的关键性句子,并了解这些句子在课文中的作用; 二、在分析关键性句子的基础上,画出文章的说明顺序结构图; [Overall Reading Thinking] Reading this text, we should firmly grasp the following three questions: First, read through the full text, figure out the key sentences of the paragraph (level), and understand the role of these sentences in the text; Second, in the analysis Based on the key sentences, draw a description of the order structure of the article;