Q2. What is the function of the first sentence in 3rd paragraph? It connects the second paragraph, continuing the subject, the development of ancient Maritime Silk Road and also severs as the topic sentence of third paragraph. Q3. What is the function of the first sentence in 4th paragraph? A transitional sentence making a turn of the discussion from ancient times to the current. Note the writing technique: one simple sentence makes a transition crossing hundreds of years. Q4. What is the function of the first sentence in the 5th paragraph? To serve as a transitional sentence expanding the topic to include sea explorations beyond trade and cultural exchange. Q5.How is para.6 related to the previous ones? It follows the previous discussion of sea explorations in the past and the present, and further pushes it to sea explorations in the future. Q6: How are the sentences connected in each paragraph? And how are paragraphs connected? Looking back on the first paragraph, then summarize the writing skill used in the expository essay: The text has four parts, and each part is a layer of meaning: topic introduction, the past, the present, and the future. So there is a clear line of time order running through the article and the first sentence is extremely important when giving information on a subject, leading the topic to the point the author wants to stress. Note the words and sentences the author uses to make transition from one layer to another. It is an important writing skill to learn. 【設計意圖】學生再次回顧文本，重新梳理信息，分析2、3、4、5每個自然段第一句的作用，通過討論并回顧第一自然段首尾句的作用，然后自然過渡到對寫作技巧的探索，培養(yǎng)學生邏輯思維能力和謀篇布局的意識。