简述电弧产生的原因。

最容易发生食管异物的部位在（）。

A.食管第一生理狭窄

B.食管第2生理狭窄

C.食管第3生理狭窄

D.食管第第4生理狭窄

E.不能确定

     I'd like to say something about the canteen service in our school.In general,the service is________(满意)．The 1.________hall is clean and tidy.The dishes look inviting and tasted________ as well.What's

more,the workers 2.________there treat us as their friends,________makes us 3.________feel  very

happy.However,the________(价格) of 4.________the meals is a little too high.Besides,we can only have

a few dishes to c________from and the canteen is5.________ ________(拥挤)．As a result, we often

have to 6.________stand in line for a long time________we can get  7.________the  meal. You could

understand what difficulty we________in dealing with the three meals  every 8.________day .May  I

suggest  something________done  to  9.________  s________ the problems so that we can all enjoy

10.________our meals at school?

（)切断风流又不准行人和车辆通行或封闭已采区和盲巷等设施的建筑物叫密闭墙。

现象和本质是揭示（）

A、事物的外部矛盾和内部矛盾相互关系的一对范畴

B、事物的内在要素和表现方式的一对范畴

C、事物的外在联系和内在联系的一对范畴

D、事物的先后相继、彼此制约的一对范畴

已知短期国库券利率为4%，纯利率为2.5%，市场利率为7%，则风险收益率和通货膨胀补偿率分别为( )。

A．3%和1.5%

B．1.5%和4.5%

C．-1%和6.5%

D．4%和1.5%