Find the Length of the Curve $r = 6 \theta , 0 \leq \theta \leq \pi$

Multiple Choice

Find the length of the curve.
-The spiral $r = 6 \theta , 0 \leq \theta \leq \pi$

A) 36
B) $3 \left( \pi \sqrt { \pi ^ { 2 } + 1 } + \ln \left( \pi + \sqrt { \pi ^ { 2 } + 1 } \right) \right)$
C) $6 \left( \sqrt { \pi ^ { 2 } + 1 } + \ln \left( \frac { 1 + \sqrt { \pi ^ { 2 } + 1 } } { \pi } \right) \right)$
D) $16 \left( \left( \pi ^ { 2 } + 1 \right) ^ { 3 / 2 } - 4 \right)$