A moving charged particle enters a magnetic field at right angles to the direction of the field. Which of the following statements about the charged particle's kinetic energy is false?
a. The EK remains constant because no work is done on the charged particle by the magnetic field.
b. The EK remains constant because the force exerted on the charged particle by the magnetic field is always perpendicular to the velocity.
c. The EK remains constant because the speed of the charged particle remains constant.
d. The EK remains constant because the velocity of the charged particle remains constant.