The question asks, "What does $f(g(x))$ represent in function composition?"

The correct answer is:

a. Function $f$ is composed of function $g$

In this context, $f(g(x))$ means you first apply function $g$ to $x$, and then apply function $f$ to the result of $g(x)$. This is known as composition of functions.

Let me know if you need more details or have any questions.

Here are five related questions to expand on this topic:

1. How do you compute $f(g(x))$ if $f(x) = x^2$ and $g(x) = x + 1$?
2. What is the difference between function composition and addition of functions?
3. Can function composition be commutative? Why or why not?
4. How do you decompose a function into two simpler functions?
5. How would you graph the composition of two functions?

Tip: When composing functions, always apply the inner function (the one inside the parentheses) first, then the outer function.