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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

写句子

把下列句子先改写成“把”字句，再改写成“被” 字句。 

(1)人们称小草为大力士。 

                                                                                                        

(2)海风刮得梧桐树东倒西歪。

                                                                                                         

(3)狡猾的狐狸欺骗了凶恶的老虎。 

                                                                                                       

(4)他在操场上找到了丢失的钢笔。

                                                                                                        

(5)奇妙的猪笼草吃掉了一条蜈蚣。 

                                                                                                       

(6)齐着船舷的菜叶和垃圾填没了这只船和那只 船之间的空隙。 

                                                                                                       

(7)一辆马车无情地轧断了小珊迪的腿。 

                                                                                                       

(8)一大滴松脂滴下来，正好包住了一个苍蝇和一个蜘蛛。

                                                                                                        

(9)下了一场大雪，地里的害虫都冻死了。 

                                                                                                         

(10)母亲带小妹妹到儿童娱乐场去散步了。

                                                                                                        

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单项选择题 B型题

治疗脚气病及多发性神经炎等（）

A.维生素A

B.维生素B1

C.维生素K3

D.维生素B2

E.维生素B6
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