Answer :
a)It is possible for the magnetic force on a charge moving in a magnetic field to be zero. The force acting on the charge is zero when a charge is moving in the same or opposite direction of the magnetic field. When a is charge moving parallel in the same direction of the magnetic field, then the magnetic force is zero.
b)It is not possible for the electric force on a charge moving in an electric field to be zero. If there's a charged particle in a magnetic field, it's impossible for this force to become zero.
c)It is not possible for the resultant of the electric and magnetic forces on a charge moving simultaneously through both fields to be zero. The magnetic force can be zero but the electric force cannot be zero because it is not affected by the motion of the particles.
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