When I saw a big handmade signboard "Welcome Yuxin" at the airport,I knew I had found a caring family at the other side of the world -- the United States. My host mom had already decorated   my room for me. There was a doll on one side of the room,and a bookcase full of books on the other -- they had heard I loved reading. Mom had also prepared a keyboard for me,since she knew that I played the piano. My life in the family did not go so well at first. Because I am the only child in my family in China,I was not used to having two younger kids -- Zachary and Grace--running around me yelling   all the time. Mom had a serious talk with me about this problem on a Sunday afternoon. She told me,"You can't just come home from school every day,go to your room and do your homework. You need to be a part of this family. You need to play with my kids for at least an hour. " This rule was very annoying at first. I did not have much experience playing with children. However,the more time I spent with the kids,the more I grew to love them. We played games and read books together. I even taught them Chinese. Thanks to Mom's rule,I began to feel like I was really part of the family. Mom also inspired me to live a healthier life. She got up early every morning to go running. On weekends,she took the whole family to visit parks or go camping. I did not like sports much when I was back home,but now I love to join all kinds of sports. I am healthier and more confident too. With my American family,I found joy and laughter. I learned to live with energy and optimism  ,thanks to the care and responsibility of my loving American parents. The passage is mainly about   _  .
the cultural differences Yuxin experienced in America how Yuxin learned to get along with younger kids in America how much Yuxin's caring host family in America changed her various difficulties Yuxin met in America