问题 选择题

一氧化碳和二氧化碳性质不同的根本原因是它们的(  )

A.相对分子质量不同

B.分子构成不同

C.用途不同

D.组成元素不同

答案

一氧化碳和二氧化碳的组成元素相同,但是分子构成不同,所以化学性质不同.

故选B.

完形填空
完形填空。
     Christmas will come soon. The radio stations (广播电台) are playing Christmas music, and the stores  1  
very busy. People are doing their Christmas shopping. Many families have got Christmas trees  2  their homes
already.
     At this time of the year people make or  3  presents for their families. Lisa is going to buy a new book for
her elder sister. Her elder sister likes  4 . Her families usually get together  5  Christmas Day. Her elder sister
lives in another city far away,  6  she always come by plane.  7  is going to arrive on Christmas Eve. Then Lisa
is going to put a  8  in the living room, and put the presents under the tree. They don't open them until
Christmas  9 . They are very  10  to receive (收到) presents.
( )1. A. be     
( )2. A. to     
( )3. A. bring  
( )4. A. swimming 
( )5. A. on     
( )6. A. so     
( )7. A. He     
( )8. A. book   
( )9. A. evening 
( )10. A. busy  
B. are           
B. at            
B. play          
B. shopping      
B. in            
B. then          
B. It            
B. Christmas tree
B. afternoon     
B. happy         
C. is     
C. from   
C. take   
C. reading
C. at     
C. but    
C. They   
C. chair  
C. morning
C. sad    
D. have 
D. on   
D. buy  
D. have 
D. of   
D. and                         
D. She  
D. desk 
D. night
D. kind 
单项选择题