1. Time background: You can introduce the historical background of the spirit of reply. For example, in the absence of modern communication tools in ancient times, people communicated through letters, which was very important at that time.
2. Social background: you can introduce the cultural characteristics and values of the society at that time. For example, in ancient times, people paid more attention to respect and gratitude to each other in correspondence, which also promoted the formation of the spirit of reply.
3. Character background: You can introduce some famous people who have the spirit of replying to letters in history, such as Bai Juyi, a poet in the Tang Dynasty. He always replies in time after receiving letters from others, and the content of the reply is very wonderful. This spirit of reply has become an example for future generations to learn.