What explanation method does the article use to analyze the characteristics of Zhaozhou Bridge? In what order?

Zhaozhou Bridge was one of the most famous bridges in ancient China and was known as the "First Bridge of Stone Arches in a Thousand Years". When analyzing the characteristics of Zhaozhou Bridge, the article uses the method of comparison. Compared with other stone arch bridges, the uniqueness of Zhaozhou Bridge was highlighted, such as its early construction, solid structure, and large scale. According to the order of explanation, the article first introduced the historical background of Zhaozhou Bridge, namely the time of its construction and the geographical location of Zhaozhou Bridge. Then the article showed the appearance of Zhaozhou Bridge, including the pier, vault, bridge deck and so on. Then the article introduced the internal structure of Zhaozhou Bridge, including the construction of the pier, the design of the vault and the way of laying the deck. At last, the paper discussed the significance of the construction of Zhaozhou Bridge, that is, it made an important contribution to the development of ancient Chinese bridge construction. Through this order of explanation, the article clearly shows the characteristics of Zhaozhou Bridge so that readers have a comprehensive understanding of Zhaozhou Bridge.