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钠是一种很活泼的金属，常温下极易跟氧气、水等物质发生如下反应：

4Na+O2═2Na2O，Na2O+H2O═2NaOH，2Na+2H2O═2NaOH+H2↑．若将一小块金属钠长期放置在空气中，经一系列变化后，最终得到的物质可能是______（写化学式），钠与水反应在化学基本反应类型中，属于______反应．

答案

Na的性质活泼，易与空气中氧气反应生成Na2O，Na2O易与水反应生成NaOH，NaOH吸收空气中的CO2生成Na2CO3．钠与水反应生成氢氧化钠和氢气，一种单质和一种化合物反应生成另一种单质和另一种化合物，属于置换反应．

故答案为：Na2CO3；置换．

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Hi Cindy,
     Please don't worry if you feel a little strange around boys. You are in the process of   1   from a little girl
into a young womman and there are   2   called hormones (荷尔蒙) that are chaIlging not only your body but
your   3  . For example, you say you used to feel at ease   4   boys and you would usually run and fight one
another for   5  . That was Cindy, the little girl. The   6   woman doesn't want to fight boys or even run with
them   7   your interests are chaIlging. That is what is making you feel strange and it is also   8   to the other
girls around you and also to the boys. Your life is   9   a different stage but you should understand that this is
(a)  10  normal, and (b) something that will pass quickly.
     I think you should again try to  11  amund boys. You can still talk with them about  12  you like including
sports, movies, web sites and celebrities (名人). I  13  that you not try to fight with them, however, because
the  14  are becoming much bigger and stronger. I think you will find that you will  15  being with boys but
that your feelings will be different from the  16  they used to be I know you are not supposed to hve a  17  
while you are still in school in China, but if you start to find some boys very handsome and you are strongly 
 18  to some of them, don't be surprised.  19 , this is all very normal. For now, you should  20  your school
work, though you will find that some boys are attracted to you. This will be a new adventure for you and my
best advice is to relax and enjoy it. 
     Good luck!
                                                                                                                                                   Brad

( )1.A. starting  
( )2.A. cells     
( )3.A. mind      
( )4.A. with      
( )5.A. praise    
( )6.A. brave     
( )7.A. before    
( )8.A. referring 
( )9.A. entering  
( )10.A. hardly    
( )11.A. play      
( )12.A. somebody  
( )13.A. recommend 
( )14.A. girls     
( )15.A. hate      
( )16.A. model     
( )17.A. boyfriend 
( )18.A. opposed   
( )19.A. Rather    
( )20.A. depend on  		B. changing   
B. nutritions 
B. head        
B. for         
B. honor      
B. unique     
B. because    
B. appealing  
B. setting    
B. possibly    
B. relax      
B. anybody     
B. demand      
B. adults     
B. enjoy      
B. standard    
B. girlfriend 
B. attracted  
B. Besides     
B. decide on       		C. surviving  
C. chemicals  
C. life       
C. against    
C. good       
C. smart      
C. until      
C. happening  
C. reflecting 
C. perfectly  
C. date       
C. something      
C. command    
C. boys        
C. avoid      
C. style      
C. degree     
C. exposed    
C. Again      
C. agree on    		D. ranging        
D. objects        
D. study           
D. without         
D. fun             
D. young          
D. when           
D. pointing       
D. representing               
D. nearly         
D. fool           
D. anything       
D. determine      
D. kids           
D. regret         
D. way            
D. job            
D. accustomed     
D. Afterwards     
D. concentrate on 
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单项选择题

下列各个关于肛瘘的说法中，哪个是不正确的（）

A.肛瘘属自限性疾病，可以自愈

B.肛瘘主要侵犯肛管，很少累及直肠

C.内口位于齿状线附近，外口位于肛周皮肤上

D.肛管括约肌间型是最常见的一种肛瘘

E.高位肛瘘是指瘘管在外括约肌深部以上
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