什么叫电枢反应？

A Policeman and a Thief  

One day a policeman was taking a thief to the city . On the way , they saw a shop . The thief said . “ Let me go into the shop to buy some bread . We can eat it in the train . ”

The policeman agreed . The thief went into the shop and ran out of the back door . When the policeman knew that , he began to look for the thief everywhere . At last the policeman caught(抓获) thief again . They went on to the city . On the way they came to the same shop . The thief wanted to buy some bread again . “Oh , no . ” said the policeman , “You did that before , and you ran away . This time I^’ll go into the shop and buy bread . You must wait here for me . ”

小题1:What was the policeman doing one day ?

A．Catching a thief with others .

B．Doing nothing.

C．Taking a thief to the city .

D．Walking go the city by himself .小题2:On the way the thief asked to         .

A．buy some food to eat .

B．let him free .

C．take a rest .

D．walk slowly .小题3:When the thief went into the shop , he ran out of        .

A．the back door .

B．the back window .

C．the front door .

D．the front window .小题4:When the thief ran away the first time , what did the policeman do ?

A．The policeman caught the thief again .

B．The policeman looked for the thief . but he didn^,t find him .

C．The thief was caught again by other policemen .

D．The policeman went back without(没有) the thief .小题5: From the last three sentences, we know that the policeman was very        .     

A．brave

B．careful

C．clever

D．foolish

使用倒扣价格方法估定进口货物关税完税价格时，应扣除的项目有（）。

A.境内销售利润

B.进口关税和进口消费税

C.运抵境内输入地点前的运保费

D.运抵境内输入地点后的运保费

如图是CsCl晶体的晶胞结构（晶体中最小重复单元），已知晶体中两个最近的Cs^＋核间距离为a cm，氯化铯的式量为M，N_A为阿伏加德罗常数，则氯化铯晶体的密度为（  ）。

A．g·cm^－3

B．g·cm^－3

C．g·cm^－3

D．g·cm^－3

有一种恒定的ＥＰＲ推力关系，只要满足：（）

A.大气压力和大气温度是恒定的

B.大气温度和Ｐs₄是恒定的

C.大气温度和喷气喷嘴面积是恒定的

D.大气压力和喷气喷嘴面积是恒定的