A particle moves in a region having a uniform magnetic field and a parallel, uniform electric field. At some instant, the velocity of the particle is perpendicular to the field direction. The path of the particle will be
The region has a uniform magnetic field and an electric field.
Formula used: Lorentz’s force is given by
Where F is Lorentz’s force
q is electric charge 
E is electric field strength
B is magnetic field strength
V is velocity
The electric field will accelerate the particle to move in the direction of the magnetic field. Magnetic field will always change the direction of velocity of a particle. Because of these the particle will move in a helix path with non-uniformity. So option D is correct.
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