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卷标号为16—25的相应位置上。

I have met many interesting people. I'll tell you about one of them. Many years ago, when I worked   16 a volunteer at Stanford Hospital, I got to know a little girl    ___17____ (name) Liza who was suffering from a rare and serious disease. Her only chance of  _18___ (recover) appeared to be a blood transfusion from    19___  five-year-old brother,    20_  had survived the same disease and developed the antibodies needed to combat the illness. The doctor explained the situation to her little brother, and asked the boy   __21  he would be willing to give his blood to his sister. I saw him hesitate for a moment    before taking a deep breath and saying, "Yes, I'll do it if it will save Liza."

As the transfusion progressed, he lay in a bed next to his sister,  22  (smile).   __23_  then his face grew pale and his smile faded. He looked at the doctor and asked with   24__  trembling voice, "Will I start to die right away?"

Being young, the boy had misunderstood the doctor. He thought he was going to have to give her  25_ his blood.

教育的构成要素有哪些简述教育各构成要素在教育活动中的地位．