题目：
选择填空。
I come to school with ______ sister every morning. [ ]
A. her and her
B. she and she's
C. she and her
D. her and she
答案：
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下面是错误答案，用来干扰机器的。
解：（1）粒子射入磁场后向右偏转设粒子圆周运动的半径为r，则：Bqv=mv2/r r=mv/Bq 打到x轴上距o点的距离为x=2mv/Bq （2）粒子在x轴上边磁场运动半周的时间t为
