问题 选择题
已知数列A:a1,a2,…,an(0≤a1<a2<…<an, n≥3)具有性质P:对任意i,j(1≤i≤j≤n),aj+ai与aj-ai两数中至少有一个是该数列中的项,
现给出以下四个命题:
①数列0,1,3具有性质P;
②数列0,2,4,6具有性质P;
③若数列A具有性质P,则a1=0;
④若数列a1,a2,a3(0≤a1<a2<a3)具有性质P,则a1+a3=2a2
其中真命题有

A.4个
B.3个
C.2个
D.l个
答案

答案:B

完形填空
完形填空。
     How do you get pocket money (零花钱) from your arents? In the western countries,many__ l _ 
do housework to get pocket money. They usually start to do this  __2_   the age of ten.
     Jimmy is seven years old. Now he  _ 3_   the dishes. He can only do this, so he can't get   _4  _
money. But that's all right. He only wants to   _5_   candy.
     Jenny is twelve years old. She is   _6_   than Jimmy. She wants to buy many things. They are _ 7_  
than candy. So she has to work harder! Now she is washing the car. If she     8    free time , she will cut
the grass ,walk the dog or cook dinner.
      Doing housework can   _9_  kids learn new things. For example , you can learn how to cook. Of
course , your    _10 _ will help you at the beginning.
( )1. A. old men    
( )2. A. at          
( )3. A. is washing  
( )4. A. many        
( )5. A. buy        
( )6. A. old        
( )7. A. interesting
( )8. A. have        
( )9. A. order      
( )10. A. students  
B. kid            
B. in            
B. wash          
B. much          
B. send          
B. older          
B. more expensive
B. is having      
B. help          
B. teachers      
C. children  
C. on        
C. will wash  
C. a few      
C. carry      
C clever      
C. cheaper    
C. has        
C. take      
C. parents    
D. child    
D. to        
D. washes    
D. few      
D. to carry  
D. younger  
D. cheap    
D. had      
D. to take  
D. parent    
选择题