Many years ago, when I was working as a volunteer at a hospital, I got to know a little girl named Lisa. The poor little girl had a very serious disease and was dying. The doctor had done his best but no medicine really worked. The only chance to save her seemed to be a blood transfusion  from her five-year-old brother. The little boy had the same disease before and had developed the antibodies  to fight the illness. The doctor talked to the little boy about what they planned to do, and asked him if he would be willing to give his blood to his sister. I saw him hesitate  for a moment. He took a deep breath and said, "Yes, I'll do it if it can save Lisa." As the transfusion was going on, the little boy lay quietly in bed next to his sister. He looked at her and smiled all the time. When everything was done and the colour returned to his sister's face, his smile disappeared and he looked a little afraid. He looked up at the doctor and asked, " Will I start to die now?" He was too young to understand the doctor. He thought he would have to give all his blood to his sister, but he agreed. The writer still remember the story many years later   _  .
because the little girl had a very strange disease because the sister and brother had the same disease because the doctor saved the little girl's life because of what the boy did for his sister