Passage Three
篇章三

Take care of your teeth and your teeth will take care of you.
好好保护你的牙齿，牙齿不会亏待你的。
Your teeth are a living part of your body. They have nerves and blood vessels.
牙齿是身体的有机部分。他们也有神经和血管。
Diseased teeth can cause pain, die and fall out.
龋齿会疼痛、死亡，然后脱落。
Plaque is the main enemy of healthy teeth. Everyone has plaque.
牙斑是一口好牙的劲敌。每个人都有牙斑。
It is a sticky colorless film that coats the teeth.
它是一种无色的黏着薄膜，覆盖在牙齿上。
Plaque is always forming on the teeth, especially at the gum line.
牙斑总是在牙齿表面形成，牙龈线上尤其常见。
If plaque is not removed, it builds up and gets under the gum line.
如果不把牙斑清掉，它就会一点点累积起来，侵蚀牙龈线。
Plaque that is left on the teeth for some time hardens; the result is tooth decay and gum disease.
被留在牙齿表面的牙斑，一段时间以后变硬，最终导致蛀牙和牙周炎。
The bacteria in plaque live on sugar.
牙斑中的细菌靠糖类生存。
They change sugar into acids, which break down the tooth's harder outer covering.
他们把糖转化成酸，酸会分解坚硬的牙齿外壳。
If left untreated, decay goes deeper and deeper into the tooth.
如果对之放任不管，牙齿会从外到里一点点坏掉。
After a while, the decay reaches the nerves and blood vessels of the inner tooth.
一段时间以后，牙齿内部的神经和血管也被腐蚀。
By the time this happens, the tooth has probably started to ache.
到了这个时候，就会牙疼了。
In addition to tooth decay, there are also gum diseases to watch out for.
除了蛀牙以外，还得小心牙周炎。
The bacteria in plaque make poisons that attack the gums.
牙斑中的细菌会产生损伤牙龈的毒素。
Small pockets form around the teeth.
牙齿四周会形成小的带状物。
The pockets trap more bacteria and food particles.
这些带状物储存越来越多的细菌和食品的残留物。
Finally, the bone supporting the teeth is attacked and starts to shrink.
最后，支撑牙齿的骨质被侵蚀，逐渐萎缩。
Teeth become loose and may fall out. Adults lose most teeth this way.
牙齿松动，还有可能脱落。成人的牙齿大多都是这么变没的。
Keep your mouth healthy. When you brush your teeth, do a good job.
保持口腔健康。刷牙时，仔细点儿！

Questions 22 to 25 are based on the passage you have just heard.
根据你刚才听到的篇章，回答22至25题。
Question 22. What does the speaker say about our teeth?
问题22. 关于牙齿，说话者提到了什么？
Question 23. What does the speaker say about plaque?
问题23. 关于牙斑，说话者说了些什么？
Question 24. Why is sugar harmful to teeth?
问题24. 为什么糖会损害牙齿？
Question 25. What causes adults to lose most of their teeth according to the speaker?
问题25. 根据谈话者所说，是什么导致成人的大部分牙齿变没的？