Bill Smith is an American worker. He and his family lives in a big city near the Great Lake. He works in a car factory. His wife, Helen, doesn't work in factory. She teaches English in a middle school. They have three children, a boy and two girls. The boy goes to school. The girls are in a kindergarten(幼儿园) .

    This year there isn't much work in the factory. Bill works only three days a week. He doesn't get much money. He does other work to get enough money for the family. He cleans out the city swimming pool in the evening. He thinks it's very fun. He can enjoy free swimming in the pool every day. He likes this new job.

    Flies(苍蝇) are one of the most dangerous enemies of human. They are dangerous because they carry diseases(疾病) , Flies do not care whether the food they eat is dor clean. The food they like best is othe dirtiest that can be found. Then they may finto a house where good clean food is kept and begin to walk all over it and eat it. Soon the good clean food becomes unfit(不合适) for people to eat. Often a person who is preparing fdoes not realize that it is unfit for people to eat, so the food is put on the tand eaten. Those who eat such food become dangerously ill. That's why we must get rid of(消灭) flies.