Passage 29    根据短文内容回答问题

　　John is a school boy and he is only eight years old. One day, his teacher asks him, "John, why didn't you come to school yesterday?" "I went to see the dentist because of my toothache(牙痛)," John answers. "Oh, I'm sorry to hear that. Is the tooth aching now?" the teacher asks. "I don't know. The dentist(牙医) left(漏) it in the hospital."

　　1.    Why didn't John come to school yesterday?

　　2.    Why did John go to see a dentist?

　　3.    Should we clean our teeth every day?