For the Given Functions F and G , Find the Indicated

Multiple Choice

For the given functions f and g , find the indicated composition.
- $\begin{array} { l } f ( x ) = x ^ { 2 } + 6 , \quad g ( x ) = x ^ { 2 } - 6 \\( f \circ g ) ( x ) \end{array}$

A) $x ^ { 4 } - 12 x ^ { 2 } + 42$
B) $x ^ { 4 } + 12 x ^ { 2 } + 30$
C) $x ^ { 4 } + 30$
D) $x ^ { 4 } + 42$