A: ① In terms of artistic structure, it produces dramatic effect through sharp turn, and finally ends with singing, which has a long aftertaste and is intriguing; ② In emotional expression, Du Fu's deadpan was used instead of crying, and love singing was used instead of complaining, which strengthened the performance of suffering; (3) The characters not only show Du Fu's free and easy, but also reflect the depth of his real pain, which makes Du Fu's image fuller; ④ Ideological, from criticizing the darkness of social reality to expressing Du Fu's belief in pursuing a free life, deepened the theme of his works.