Let $f ( x ) = 3 x , g ( x ) = x + 1$

Let $f ( x ) = 3 x , g ( x ) = x + 1$ . Find the composite function.
$$( g \circ g ) ( x )$$

A) $\quad ( g \circ g ) ( x ) = 3 x + 1$
B) none of the above
C) $\quad ( g \circ g ) ( x ) = 3 x + 3$
D) $\quad ( g \circ g ) ( x ) = 9 x$
E) $\quad ( g \circ g ) ( x ) = x + 2$