Four +ve point charges of same magnitude (Q) are placed at four comers 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<<L), then

• A

  it oscillates along the Z-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