Find the Distance Traveled by a Particle Moving on the Curve

Multiple Choice

Find the distance traveled by a particle moving on the curve given by $\vec { r } ( t ) = \langle \sin ( 3 t ) , \cos ( 3 t ) \rangle$ find the displacement vector as $t$ goes from $t = 0$ to $t = \pi$

A) $\pi \sqrt { 3 }$
B) $3 \pi$
C) $2$
D) $2 \pi$