问题 选择题
如图所示为一磁流体发电机示意图,A、B是平行正对的金属板,等离子体(电离的气体,由自由电子和阳离子构成,整体呈电中性)从左侧进入,在t时间内有n个自由电子落在B板上,则关于R中的电流大小及方向判断正确的是(  )

A.I= ,从上向下

B.I= ,从上向下

C.I= ,从下向上

D.I= ,从下向上

答案

答案:A

写句子

按要求完成句子。  

1.维吾尔的姑娘很漂亮。维吾尔的姑娘能歌善舞。(用关联词连成一句)

                                                                                                                     

2.人们为姑娘们俊俏的容貌、婀娜的舞姿、优美清新的唱腔赞叹不已。 (缩句)

                                                                                                                 

3.这是美好快乐的日子。(改为感叹句) 

                                                                                                                 

4.我很难忘记那次藏戏演出的情景。(改为反问句)

                                                                                                                  

5.除夕真热闹。(扩句)

                                                                                                                  

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