背诵。

1. Young children might            Superman or Batman while adults might picture a doctor or police officer.

2. Beth            a respiratory problem which made it difficult for her to breathe.

3. She grew up in and out of hospitals where she                 devices to help control her illness.

4. But she was determined, and when her eleventh birthday            , Beth was there to          her candles.

5. She proved the doctors wrong but, even though she lived past the       , she still wasn't       .

6. Beth went through several more years of nurses and doctors poking her like      but she never

    complained.

7. With all she had to deal with, you would think she would be too busy to listen to her

     friends'        -nevertheless she always found time

简述扩散式燃烧器的优点