Xue Feng (L) talks with her colleague on a train on Jan. 18, 2019. Xue Feng is a train conductor of the China Railway Shanghai Group Co., Ltd, whose husband is a policeman. Because of their jobs, they can't accompany their son zhuangzhuang all the time. Every time when Xue Feng has to leave home for work for a few days, she will write an excuse note to zhuangzhuang to express her regret. And every time when zhuangzhuang receives an excuse note from his mother, he will put it in his "treasure box" . Now he has received 21 excuse notes from his mother, and he knows he will keep on receiving them in the future. However, zhuangzhuang says he will not cry, because he has grown up. (Xinhua/Li Bo)