2. 外语
  3. A、It has to be removed in time by a dentist. B、It is a rare oral disease among old people. C、It contains many nerves and blood v

A、It has to be removed in time by a dentist. B、It is a rare oral disease among old people. C、It contains many nerves and blood v

admin2019-03-12  34
问题  
Take care of your teeth and your teeth will take care of you. Your teeth are a living part of your body. They have nerves and blood vessels. Diseased teeth can cause pain, die and fall out. Plaque is the main enemy of healthy teeth. Everyone has plaqu
选项 A、It has to be removed in time by a dentist.
B、It is a rare oral disease among old people.
C、It contains many nerves and blood vessels.
D、It is a sticky and colorless film on the teeth.
答案D
解析 短文中提到，牙斑是牙齿表面一层粘粘的无色层，故答案为D。
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大学英语四级

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