Four point `+ve` charges of same magnitude`(Q)` are placed at four corners of a rigid square frame as shown in figure. The plane of the frame is perpendicular to `z`-axis. If a `-ve` point charge is placed at a distance `z` away from the above frame `(z lt lt L)` then

Options

A. – ve charge oscillates along the axis
B. It moves away from the frame
C. It moves slowly towards the frame and stays in the plane of the frame
D. It passes through the frame only once.