阅读理解。
     A smile will tell people around you that you are a kind and friendly person. However, many people
 don't smile because they think they have ugly teeth. For example, one of my classmates, Mike, doesn't
 have very nice teeth, so that is why he seldom opens his mouth. He even says that he has lost confidence
 because of his teeth. So it is very important for us to look after our teeth. In fact, a lot of people have this problem. Some people inherit teeth problems from their parents, while others' teeth are damaged because
  of bad habits, like heavy smoking, eating too much sugar or not brushing teeth often. If your teeth are in
 bad shape, you should see a dentist and ask for help. They can help improve your teeth and tell you how
 to take care of them.
     Smiling can help you to feel more confident and make other people think of you as a more friendly
 person. If' you want to keep healthy, you should not only smile but also laugh. An Indian doctor called
 Kataria said that young children should laugh about 300 times a day, while adults should laugh between 7
  and 15 times a day. So please take this chance to smile and laugh now!
1. What has made Mike lose his confidence?
    A. His bad habit.
    B. His bad teeth.
    C. Not smiling.
    D. Eating too much sugar.
2. Many people don't smile because _____.  
    A. they don't like smiling
    B. they think they are ugly
    C. their teeth are not beautiful
    D. they can't open their mouths
3. What can a dentist do according to the passage?
    A. A dentist can help improve your bad teeth.
    B. A dentist can tell you how to take care of your bad teeth.
    C. A dentist can tell you how to brush your teeth.
    D. Both A and B．
4. If you want to keep healthy, you had better _____.
    A. not smile often
    B. laugh all the time
    C. neither smile nor laugh
    D. smile and even laugh often
5. How many times should a child laugh every day in doctor Kataria's opinion?
    A. Either 300 or 30 times a day.
    B. Between 7 and 15 times a day.
    C. About 300 times a day.
    D. Only 30 times a day.