Assume that $f$ is an even function, $g$ is an odd function, and both $f$ and $g$ are defined on the entire real line $\mathbb{R} .$ Which of the following (where defined) are even? odd?
a. $f g \quad$ b. $f / g \quad$ c. $g / f$
d. $f^{2}=f f \quad$ e. $g^{2}=g g \quad$ f. $f \circ g$
g. $g \circ f \quad$ h. $f \circ f \quad$ i. $g \circ g$