Let $r(x) = {\tan^{2}\!\left(x\right)}$. Which of the following best describes its fundamental algebraic structure? A. A composition $f(g(x))$ of basic functions
B. A sum $f(x)+g(x)$ of basic functions
C. A product $f(x) \cdot g(x)$ of basic functions
D. A quotient $f(x)/g(x)$ of basic functions where $f(x) =$ $g(x) =$