帮我生成解说视频---**Question 8:**
**Question Stem:**
8.・一匀强电场的方向平行于 xOy 平面，平面内 A 点和 B 点的位置如图所示。电荷量为 +q、-q 和 +2q 的三个试探电荷先后分别置于 O 点、A 点和 B 点时，电势能均为 E_p (E_p > 0)。下列说法正确的是 (□□)。
**Diagram Description:**
* Type: 2D Cartesian Coordinate System.
* Axes: X-axis (horizontal, labeled 'x', positive direction to the right), Y-axis (vertical, labeled 'y', positive direction upwards). The origin is labeled 'O'.
* Points:
* O: Origin (0, 0).
* A: Point on the x-axis, labeled 'A (d, 0)'.
* B: Point in the first quadrant, labeled 'B (d, 3/4 d)'.
* Lines: Solid lines for the axes and segments OA and part of the segment from A perpendicular to the x-axis. Dashed lines from B perpendicular to the x and y axes, intersecting at (d, 3/4 d).
**Options:**
A. ・OA 中点的电势为零
B. ・电场的方向与 x 轴正方向成 60° 角
C. ・电场强度的大小为 $\frac{\sqrt{2}E_p}{qd}$
D. ・电场强度的大小为 $\frac{2\sqrt{2}E_p}{qd}$