A particle, moving through a certain region of space, experiences a non-zero magnetic force. Which of the following is possible?
(a) A magnetic field exists in that region and changes the speed of the particle.
(b) A magnetic field exists in this region and the particle's velocity vector is parallel to the magnetic field vector.
(c) A magnetic field exists in this region and the particle is moving at right angles to the magnetic field.
(d) A magnetic field exists in this region and the particle is moving in the direction opposite to the magnetic field vector.