Solve the following math problem efficiently and clearly:

- For simple problems (2 steps or fewer):
Provide a concise solution with minimal explanation.

- For complex problems (3 steps or more):
Use this step-by-step format:

## Step 1: [Concise description]
[Brief explanation and calculations]

## Step 2: [Concise description]
[Brief explanation and calculations]

...

Regardless of the approach, always conclude with:

Therefore, the final answer is: $oxed{answer}$. I hope it is correct.

Where [answer] is just the final number or expression that solves the problem.

Problem: The functions $p(x),$ $q(x),$ and $r(x)$ are all invertible.  We set
\[f = q \circ p \circ r.\]Which is the correct expression for $f^{-1}$?

A. $r^{-1} \circ q^{-1} \circ p^{-1}$

B. $p^{-1} \circ q^{-1} \circ r^{-1}$

C. $r^{-1} \circ p^{-1} \circ q^{-1}$

D. $q^{-1} \circ p^{-1} \circ r^{-1}$

E. $q^{-1} \circ r^{-1} \circ p^{-1}$

F. $p^{-1} \circ r^{-1} \circ q^{-1}$

Enter the letter of the correct expression for $f^{-1}.$
user