如图是一个反射弧的部分结构图,甲、乙表示连接在神经纤维上的电

如图是一个反射弧的部分结构图,甲、乙表示连接在神经纤维上的电流表。当在A点以一定的电流刺激,甲、乙电流表的指针发生的变化正确的是(   

   

A.甲不偏转,乙只发生一次偏转

         B.甲只发生一次偏转,乙不偏转

         C.甲、乙都发生两次方向相反的偏转

         D.甲发生两次方向相反的偏转,乙不偏转

答案

B

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