问题 单项选择题

关于固定义齿固位体正确的描述是()

A.与全冠固位体相比,部分冠固位体需磨除的基牙牙体组织少,能够提高基牙抗力

B.嵌体固位体能有效预防基牙继发龋的发生

C.双端固定桥两端固位体固位力应接近

D.多基牙的固定义齿宜采用嵌体固位体

E.死髓基牙均应采用根内固位体设计

答案

参考答案:C

解析:双端固定桥两端基牙如固位力相差太大,固位力较弱的一侧固位体易松动,导致固定桥失败,因此两端固位体固位力应接近。全冠固位体对基牙的保护好,能够提高基牙抗力;嵌体边缘线长,易导致继发龋;多基牙固定义齿应选择固位力好的全冠固位体;死髓基牙如牙体缺损量不大时无需采用根内固位体。

阅读理解

阅读理解

     A volcanic eruption in Iceland has sent ash across northern Europe. Airlines have stopped or changed

the flights across the Atlantic Ocean, leaving hundreds of passengers stuck in airports.

     Grimsvom is one of the largest and most active volcanoes in Europe. What makes Grimsvom different

is that it lies under a huge glacier(冰川) of ice up to 12 meters thick. The hot volcano heats up the ice

above it, which then forms a layer(层)of water between the glacier and the volcano.This layer of water

puts pressure on the volcano, keeping it stable. As the water flows out from under the glacier, the pressure lifts. The lava(岩浆) from the volcano then comes up to the surface. This is exactly what happened today.

     Now, airlines have to make changes to their flights so as not to fly through the clouds of volcanic ash.

According to KLM,one of Europe's biggest airlines, airplanes cannot go under the cloud or over it. Going

through the cloud can result in ash getting stuck in the airplane's engines, causing damage to the plane.

     The eruption has also caused problems for animals in Iceland. The volcano left ash and sharp glasslike

rocks all over the countryside. Farmers are keeping their animals inside to stop them from eating

ashcovered grass or the sharp object.

  

1.What makes Grimsvom different from other volcanoes?  

A.It is below ice.

B.It lies under the sea.

C.It is the largest volcano.

D.Its lava affects the airlines.  

2.What keeps Grimsvom still?  

A.The slow flow of water.

B.The low water temperature.  

C.The thick glacier.

D.The water pressure.  

3.Which of the following is the result of the volcanic eruption?

A.People stop traveling in Europe.

B.Airlines suffer from the loss of planes.  

C.It becomes dangerous for animals to eat outside.

D.Farmers have lost many of their animals.  

4.This text is most probably taken from________.

A.a research paper  

B.a newspaper report

C.a class presentation  

D.a geography textbook

单项选择题