单项选择题

The third of March, 1887, three months before l was seven years old, was the most important day I remember in all my life. On that day, my teacher, Anne Sullivan, came to me. I felt approaching footsteps. I thought it was my mother and stretched out my hand. Someone took it, and then I was caught up and held close in the arms of the person.
The morning after my teacher came she led me into her room and gave me a doll. When I had played with it a little while, Miss Sullivan slowly spelled into my hand the word "d-o-l-l". I was at once interested in this finger play and tried to imitate it. When I finally succeeded in making the letters correctly I was filled with childish pleasure and pride. Running downstairs to my mother I held up my hand end made the letters for doll. I did not know that I was spelling a word or even that words existed, I simply made my fingers go in monkey-like imitation. In the days that followed I learned to spell in this uncomprehending way many words. But my teacher had been with me several weeks before I understood that everything has a name.
When Miss Sullivan taught the word "doll", the author was at once interested because ______.