A magnetic field of strength B exerts a force on a charge, q, moving with a speed v, to make the charge move in a circular path of radius r. Which of the following statements about the time it takes for the charge to make one complete circle, T, is true?
a. T depends on B, q and m only.
b. T depends on B, q, m and v only.
c. T depends on B, q, m, v and r.
d. T depends on B, v and r only.