A CD Has a Diameter of 12

A CD has a diameter of 12.0 cm.If the CD is rotating at a constant frequency of 4.00 cycles per second,then the period of the rotational motion is

A) 0.250 s.
B) 0.500 s.
C) 0.750 s.
D) 1.00 s.
E) 1.25 s.