This problem gives you some practice identifying how more complicated functions can be built from simpler functions.

Let $f(x)= x^3+1$and let $g(x)=x+1$. Match the functions defined below with the letters labeling their equivalent expressions.
1. $f(x)/g(x)$
2. $g(f(x))$
3. $g(x)f(x)$
4. $f(x^2)$

A. $2 + x^3$
B. $1 + x + x^3 + x^4$
C. $1 + x^6$
D. $1 - x + x^2$