Analysis: This question tests the appreciation of poetic expression techniques. Appreciating the expression skills of poetry requires an overall grasp of the content of the work, and on this basis, combined with the specific techniques you usually know, you need to appreciate the poetry. This poem is full of memories of past life and helplessness of real life. It is obvious that the author used contrasting techniques. In this way, analysis can be carried out from this.
Answer: Comparison. The second and third sentences use vivid historical facts to describe the decadent life of Chen Shubao, the last monarch of the Six Dynasties. The fourth sentence forms a strong contrast with the second and third sentences. The word "", like a cartoon, outlines the tragic ending of Jinling being conquered by the Sui soldiers, and Empress Chen having no choice but to become a frog in the well. It expresses the poet's anger and contempt for these ugly people.