Bi, that is, making an analogy, is an image comparison of things; Xing is to use other things as a starting point to cause the thing to be sung. Bixing sentence: "The mulberry trees have not yet fallen, but their leaves are lush. The doves are sighing, and there is no food for the mulberries. The mulberry trees have fallen, and they are yellow and fall." Function of Bixing: Structure: ① Insert Bixing sentence into the narrative , This avoids the straightforward narrative ② implies content ③ plays a transitional role content: ① evokes rich associations in readers. ②Create an atmosphere and set the emotional tone.