If a charged particle enters in a region where electric and magnetic field are parallel to its motion, then it will:

Explanation

Option C is correct since over here the velocity vector and magnetic field vector are in the same direction so there is no magnetic force. So the direction of the electric field is the direction of the charged particle. The charged particle can be assumed to be positive over here, so its direction will be similar to the direction of the electric field which is from higher potential to lower potential. The electric force will cause the charged particle to accelerate and thus speed up.Option A is incorrect since the velocity vector is parallel to the magnetic field vector so there will be no deflection due to no magnetic force. The charged particle will simply move in the direction of the electric field.Option B is incorrect since the velocity vector is parallel to the magnetic field vector so there will be no deflection due to no magnetic force. The charged particle will simply move in the direction of the electric field.Option D is incorrect since an assumption is applied over here which considers the charged particle as positive.So if the motion of a particle is along an electric field, the electric force will cause the charged particle to accelerate and thus speed up.