Factor the Expression Completely $6 x ^ { 2 } + 3 x ^ { 3 }$

Factor the expression completely. $6 x ^ { 2 } + 3 x ^ { 3 }$

A) $\quad 3 x ^ { 2 } ( 3 + x )$
B) $\quad 3 x ^ { 2 } ( 2 + x )$
C) $\quad 3 x ^ { 2 } \left( 2 + x ^ { 2 } \right)$
D) $\quad 3 x ^ { 2 } ( 2 - x )$