$\mathrm{A} C D$ Has a Diameter Of $12.0 \mathrm{~cm}$ If The Has

$\mathrm{A} C D$ has a diameter of $12.0 \mathrm{~cm}$ . If the $C D$ is rotating with a constant period of 0.314 seconds, then the frequency of the rotational motion is

A) $3.18 \mathrm{~Hz}$ .
B) $2.15 \mathrm{~Hz}$ .
C) $2.83 \mathrm{~Hz}$ .
D) $3.67 \mathrm{~Hz}$ .
E) $4.00 \mathrm{~Hz}$ .