阅读下面短文,根据其内容写一篇60词左右的内容概要。Adam lived with his parents in one city while his grandparents lived far away in another city. Adam's parents usually took their son to his grandparents' house during summer holiday every year and stayed there for around 20 days. Adam's grandfather loved him very much and spent a lot of time playing with him. His grandmother always cooked delicious food for him. Adam loved his stay there. This continued for years. The boy grew up over time. One day Adam said to his parents, "Now, I am old enough to go to grandparents' house alone. So, please let me go by myself. "His parents didn't agree at first but Adam insisted(坚持). They finally agreed. But they were worried about his safety. So, they taught him everything he needed to know to travel alone. The day came when Adam was to leave for his grandparents' house. And his parents came to see him off at the train station. When the boy was comfortably seated on the train, his parents got off and waited for the train to leave. While waiting, the father went to the window and kept talking to his son. He handed his son an envelope(信封) from the window and said, "Son, if you feel afraid on the way, open this and read it. It will help you to calm down. "The boy kept that envelope in his pocket carefully and said goodbye to his parents. When the train was ready to leave, the boy smiled and told his father, "I remember everything. Don't worry. "At every station where the train stopped, people kept coming and going. The boy started feeling a little lonely.
答案:One possible version:Adam's family and his grandparents live in two cities far away. (要点1) But every summer vacation, his parents take Adam to his grandparents' home. (要点2)One day, Adam said that he had grown up and wanted to go to his grandparents' home alone. (要点3)The parents were worried, but they were persuaded. (要点4)Before getting on the bus, my parents told Adam a lot and gave him a letter telling him to open the envelope if he was afraid. (要点5)