---It was dangerous to throw that bottle out of the window. You could have hurt someone.

---I’m so sorry! I _______ .

A．am not thinking

B．wasn’t thinking

C．haven’t thought

D．don’t think

如图13-9-13所示，质量为m=2×10^-15 kg、q=-3×10^-10 C的带电粒子，自A点垂直电场线方向进入有界的匀强电场，它从B点飞出时v_B=6×10³ m/s,v_B与E交角120°.已知AB沿电场线方向相距15 cm，不计重力，求：

图13-9-13

（1）U_BA的大小；

（2）粒子A到B的时间；

（3）匀强电场的宽度.