Specify the Domain Of $( g \circ f ) ( x )$

Multiple Choice

Specify the domain of $( g \circ f ) ( x )$ for the pair of functions f ( x ) = 2 x + 3 and g ( x ) = x 2 + 9.

A) $( - \infty , \infty )$
B) $( - \infty , 0 )$
C) $( - \infty , 0 ) \cup ( 0 , \infty )$
D) $( 0 , \infty )$