State the Period of the Function $y = \tan \frac { x } { 3 }$

Multiple Choice

State the period of the function:
$y = \tan \frac { x } { 3 }$

A) $5 \pi$
B) $\frac { \pi } { 2 }$
C) $6 \pi$
D) $3 \pi$
E) $4 \pi$