Bad teeth can be painful — and worse. They can even be deadly. Infections (感染）of the gums (牙龈）and the teeth can cause bacteria (细菌）to go into the blood system. Those bacteria can increase the chance of a heart attack and worsen the effects of other diseases. And adults are not the only ones at risk. For example, in 2007, doctors in the Washington area said a boy died when a tooth infection spread to his brain. They said it might have been prevented had he received the dental care (牙齿 保健）he needed. He was twelve years old.
Experts at the National Institutes of Health say good dental care starts at birth. Breast milk, they say, is the best food for the healthy development of teeth. Breast milk can help slow the growth of bacteria and acid production in the mouth.
But dentists say a baby's gums and early teeth should be cleaned after each feeding. Use a cloth with a little warm water. Do the same if a baby is fed with a bottle. Experts say if you decide to put your baby to sleep with a bottle, only give the child water.
When baby teeth begin to appear, you can clean them with a wet toothbrush. Dentists say it is important to find soft toothbrushes made especially for babies and to use them very gently.
The use of fluoride (氟化物）to protect teeth is common in many parts of the world. For example, it is often added to drinking water supplies. The fluoride mixes with enamel (法琅质)， the hard surface on teeth, to help prevent holes from forming.
31.According to the passage, bad teeth can be ____________.
A.painful  B. deadly  C.preventive  D.incurable
32.The writer uses the boy's death as an example to show that   _______?
A. not only adults but the young may suffer from teeth problem
B. babies with bad teeth can easily die
C. the doctors should be responsible for the case
D. the boy was not fed with his breast milk
33. What's the main idea of paragraph 4 and 5?
A. How to develop babies' teeth.           B. Why to protect babies' teeth
C. How to keep babies' teeth clean         D. Why to keep babies' teeth clean
34. The passage tells us that _______.
A. Enamel is most widely used to protect teeth in the world
B. Bad teeth may affect the health of adults and the young
C. Breast milk can cure babies' bad teeth
D. Babies' teeth should be brushed once per day
35.Which of the following can be used as the title of the passage?
A. Concerns for Healthy Teeth of the Young  B. Importance of Healthy Teeth of All
C. Causes of Teeth Problem               D. Solutions to Teeth Problem