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

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．