The correct answer is **(D) Execute oscillatory but not simple harmonic motion**

**Solution**

Motion is simple harmonic only if the charge Q is released from a point not very far from the origin on the x-axis.

Else where, motion is periodic but not simple harmonic.

#### The motion of Charged Particle in Electric Field

If a charged particle of charge Q is placed in an electric field of strength E, the force experienced by the charged particle = EQ.

- The acceleration of the charged particle in the electric field, a = EQ/m.
- The velocity of the charged particle after time t is = (EQ/m)t if the initial velocity is zero.
- The distance travelled by the charged particle is S = (1/2) × at2 = 1/2(EQ/m) × t2 if the initial velocity is zero.