A negatively charged particle travels parallel to magnetic field lines within a region of space. Which one of the following statements concerning the force exerted on the particle is true?
A. The force is directed perpendicular to the magnetic field.
B. The force is perpendicular to the direction in which the particle is moving.
C. The force slows the particle.
D. The force accelerates the particle.
E. The force has a magnitude of zero newtons.