Solve this:
Two equal negative charges-q, are placed at point (0,a) and (0,-a) on y axis, one positive charge q at rest is left to move from point (2a,0). This charge will be :
(1) executive S.H.M. about the origin.                            (2) oscillate but not execute S.H.M.
(3) move towards origin and will become stationary        (4) S.H.M. along x axis.