题目

一个带电粒子沿垂直于磁场的方向射入该匀强磁场，粒子的后段轨迹如图2-6所示，轨迹上的每一小段都可以近似看成圆弧.由于带电粒子使沿途的空气电离，粒子的能量逐渐减少（带电荷量不变）。从图中情况可以确定（ ） A.粒子从到b,带正电B.粒子从b到,带正电C.粒子从到b，带负电D.粒子从b到,带负电图2-6-That's the third time he's won the award in this field.-Yes. He __________ his maximum potential in the past decade.A. explored B. is exploringC. has been exploring D. has explored