Find All Zeros of the Function $f ( x ) = ( x + 6 ) ( x + 3 i ) ( x - 3 i )$

Multiple Choice

Find all zeros of the function $f ( x ) = ( x + 6 ) ( x + 3 i ) ( x - 3 i )$ .

A) $x = 6 , - 3 i , 3 i$
B) $x = - 6,3 i$
C) $x = - 6 , - 3,3$
D) $x = - 6 , - 3 i , 3 i$
E) $x = - 6$