之一

例句：

1. 1. I have one sister and one brother.
   我有一个姐姐和一个哥哥。
2. 2. She has one book in her hand.
   她手里拿着一本书。
3. 3. One day, she will become a famous writer.
   总有一天，她会成为一位著名的作家。