A particle of charge q and mass m is subjected to an electric field E = E0(1 – ax2) in the x-direction, where a and E0 are constants. Initially the particle was at rest at x = 0. Other than the initial position the kinetic energy of the particle becomes zero when the distance of the particle from the origin is
(1) √3/a
(2) √2/a
(3) √1/a
(4) a