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问题 选择题
如图所示，AB是一质量为m的均匀细直杆，A端靠在光滑的竖直墙壁上，B端置于水平地面上，杆身与竖直方向夹角为θ，杆与地面的摩擦系数为μ，保持平衡，则此时杆与地面的摩擦力为（　　）

A．mgtgθ

B．mgsinθ

C．μmg

D．μmg

答案

答案：A

完形填空
完型填空。
    John is a Canadian. He lives in a tall building. He gets up at _1_ every morning. He _2_ home at seven o'clock. And he gets to school at seven forty.
    He has _3_ classes in the morning and two in the _4_. After school, he likes to play volleyball _5_ his
classmates. He  goes  home at five  thirty _6_. He and his _7_ have  dinner _8_ home. _9_ he does his
homework. He goes to _10_ at around nine thirty.
    What a busy day!
( )1.A. six fourty
( )2.A. goes      
( )3.A. eight    
( )4.A. morning  
( )5.A. and      
( )6.A. a.m.      
( )7.A. teachers      
( )8.A. at        
( )9.A. When      
( )10.A. bed      		B. six forty
B. gets      
B. ten      
B. evening  
B. with      
B. p.m.      
B. mothers         
B. in        
B. Then      
B. the bed   		C. seven fourteen
C. comes        
C. four          
C. night        
C. to            
C. in afternoon          
C. parents      
C. out          
C. How          
C. a bed         		D. seven forty    
D. leaves        
D. twelve        
D. afternoon      
D. like          
D. in the morning                
D. students      
D. behind        
D. Why            
D. beds          
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选择题

对于分子动理论和物体内能的理解，下列说法正确的是

A．温度高的物体内能不一定大，但分子平均动能一定大。

B．一定质量的理想气体在等温变化时，内能不改变，因而与外界不发生热交换。

C．布朗运动是液体分子的运动，它说明分子永不停息地做无规则运动。

D．扩散现象说明分子间只存在斥力不存在引力。
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