搜题请搜索小程序“爱下问搜题”
问题 不定项选择

某物体t1时刻向东运动，速度大小为v，此时动能为E；由t1时刻到t2时刻这段运动过程中，物体的动能变化了2E。那么，t2时刻物体的速度可能是 [ ]

A．大小为3v，方向向东

B．大小为v，方向向东

C．大小为v，方向向西

D．大小为v，方向向西

答案

BD

多项选择题

哮喘的气道阻塞由联合因素所致，包括（）

A.气道粘膜水肿

B.气道平滑肌痉挛

C.粘液分泌增加

D.气道上皮下炎性细胞（尤其是嗜酸性细胞和淋巴细胞）浸润

E.气道上皮损伤和脱屑
查看答案
完形填空
完形填空

       The bicycle is one of the simplest (最简单的) yet most useful inventions in the world. What is most
surprising is that it was not invented earlier,   1   the great inventor Leonardo da Vinci had drawn pictures
for bicycles and also for flying machines and some other things. Those things  were not produced   2   long after he died.
       A person riding a bicycle use   3   energy(能量)to make the bicycle move, and there is no pollution
at all when you are riding. Even so, m developed   4  , most people don't travel to  work by bicycle. It is
not because the bicycles are expensive or people feel   5   if they ride to work. It's because    6   cars on
the roads becomes larger. It certainly becomes   7   to ride a bi-cycle. As a result, more people put their
bicycles away and go to work   8   their cars and, in this way, the situation(情形)is made more serious.  9   the best way to make riding safer and more popular is to create paths(开设通道)only for bicycles, and
to make   10    so difficult and expensive for drivers to take their cars into the city that they will go back
to use their bicycles.


( )1. A．although          
( )2. A．when              
( )3. A．much              
( )4. A．world            
( )5. A．comfortable      
( )6. A．the number of    
( )7. A．safer            
( )8. A．by                
( )9. A. Always            
( )10.A．it                
                                          		B．so              
B．before          
B．quite a lot of  
B．countries        
B．1ucky            
B．a number of      
B．more dangerous  
B．in              
B．May be          
B．them          
C．but              
C．since            
C．very little      
C．1and            
C．sorry            
C．this kind of    
C．much dangerous  
C．use              
C．Perhaps          
C．us               
                                		D．because         
D．until           
D．many            
D．earth           
D．tired           
D．a kind of       
D．safe            
D．drive           
D．Nearly          
D．that      
查看答案