问题 单项选择题

3/4冠牙体预备的叙述正确的是( )

A.临床牙冠长,倒凹大者,冠边缘应止于龈缘

B.上前牙切斜面由舌侧斜向唇侧

C.在切端斜面舌1/3处,做一顶角90°的沟

D.舌轴壁的倒凹不必消除,可以舌隆突为界分两段预备

E.邻沟与邻面的线角清晰,有棱角

答案

参考答案:C

解析: 牙冠长、倒凹大时,冠边缘在龈缘以上,冠覆盖区内应该无倒凹。上前牙切斜面由唇侧倾斜向舌侧,尽可能少的暴露金属。为保证修复体就位、磨合,舌轴壁的倒凹一定要磨除。邻沟与邻面的线角应清晰、无明显棱角,棱角处修复体有应力集中容易造成修复体折断。

阅读理解

阅读理解。

Dear Mom and Dad,

      I'm afraid I have some very bad news for you. I have been very naughty and the school master is very

angry with me. She is going to write to you. You must come and take me away from here. She does not

want me in the school any longer. The trouble started last night when I was smoking a cigarette in bed. As

I was smoking, I heard footsteps coming towards the room. I did not want a teacher to catch me smoking,

so I threw the cigarette away.

       Unfortunately, the cigarette fell into the waste-paper basket. It caught fire.

       There was a curtain near the waste-paper basket. It caught fire too. Soon the whole room was burning.

The master phoned the fire brigade. The school is a long way from the town and before the fire brigade

arrived, the whole school was on fire. The master said that the fire was all my fault and I must pay for the

damage. She will send you a bill for about a million dollars. I'm very sorry for this.

                                                                                                                                      Much love 

                                                                                                                                      Sarah

1. Why did Sarah write to his parents? [ ]

A. He missed them very much for they hadn't seen each other for a long time.

B. He told his parents what he had done in school.

C. He was tired of studying, and wanted to leave school.

D. He thought he was old enough to help them do something.

2. Where did Sarah smoke? [ ]

A. In the classroom.

B. In the dinning hall.

C. In the street.

D. In the dormitory.

3. Why was the school master angry with him? [ ]

A. Because he was too naughty.

B. Because he was too lazy.

C. Because he caused a big fire.

D. Because he stole something from the school.

4. According to the passage, what should the students not do? [ ]

A. They should not smoke, because smoking is dangerous to them.

B. They should not dance, because dancing would waste a lot of mone

C. They should not make friends, because making friends would take them absen

D. They should not wear expensive clothes because they would waste money.

单项选择题