阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空，并将答案填写在答题卡标号为16—25的相应位置上。
Many years ago, when I worked as a volunteer at Stanford Hospital, I got to know a little girl __16___ （name） Lisa who was suffering from a rare and serious disease．Her only chance of recovery appeared to be a blood transfusion __17___ her five-year-old brother, ___18__ had miraculously （奇迹般地） survived the same disease and had developed the antibodies （抗体） needed to fight the ___19__ （ill）．
The doctor explained the situation to her little brother, and asked the boy___20__ he would be willing to give his blood to his sister．I saw him hesitate for only a moment before taking ___21__ deep breath and saying, “Yes, I’ll do it if it can save Lisa．”
As the transfusion progressed, he lay in a bed next to his sister and ___22__ （smile）, as we all did, seeing the color returning ____23__ her cheeks．Then his face grew pale and his smile faded．He looked up at the doctor and asked with a trembling voice, “Will I start to die right away?”
Being young, the boy had ____24___ （understand） the doctor; he thought he was going to have to give her all ___25___ blood．