A、She was a professional teacher. B、She was also a blind person. C、She knew how to teach the blind. D、She did not look down upon

The name Helen Keller has had special meaning for millions of people in all parts of the world. She could not see or hear. Yet Helen Keller was able to do so much with her days and years. Her success gave others hope.
    Until she was one-and-a-half-year old, Helen Keller was just like any other child. Then, 19 months after she was born, Helen became very sick. It was a strange sickness that made her completely blind and deaf.
    From that time until she was almost seven years old, Helen could communicate only by making signs with her hands. But she learned how to be active in her silent, dark environment. The young child had strong desires. More and more, she wanted to communicate with others. Making simple signs with her hands was not enough, because she could not make people understand her.
    A teacher arrived from the Perkins Institution for the blind in Boston. Her name was Anne Sullivan. She herself had once been almost completely blind. But she had regained her sight.[25]At Perkins, she had learned the newest methods of teaching the blind.
    At first, the teacher formed words in her hand, the names of everything she touched. Then Miss Sullivan taught Helen many things — to read and write, and even to use a typewriter. But most important, she taught Helen how to think.
    Three years after Helen started to communicate with her hands, she began to learn to speak as other people did. Those first days when Helen Keller developed the ability to talk were wonderful. But they proved to be just the beginning of her many successes.
22. What is the passage mainly about?
23. Why was Helen Keller blind and deaf?
24. How did Helen communicate with others before she was seven years old?
25. Why could Sullivan teach Helen to communicate?