Which of the following statements are true? a. if the functions $f(x)$ and $g(x)$ have inverses, and $h = f \circ g,$ then the function $h$ has an inverse, and $h^{-1} = f^{-1} \circ g^{-1}.$ b. if $f(x)$ and $g(x)$ have inverses, then the function defined by $h(x) = f(x) + g(x)$ has an inverse. c. if $f(f(x)) = x$ for all $x,$ then the function $f(x)$ has an inverse. d. if $f(f(f( = x$ for all $x,$ then the function $f(x)$ has an inverse. e. if the function $f(x)$ has an inverse, and $f(x) \neq 0$ for all $x,$ then the function defined by $g(x) = \frac{1}{f(x)}$ has an inverse. f. if the function $f(x)$ has an inverse, then the function defined by $g(x) = [f(x)]^2$ has an inverse. g. if the function $f(x)$ has an inverse, and $f(x) \ge 0$ for all $x,$ then the function defined by $g(x) = \sqrt{f(x)}$ has an inverse. h. if $f(x) < f(y)$ for all $x > y,$ then the function $f(x)$ has an inverse. enter the letters of the true statements, separate d by commas. for example, if you think statements e and h are true, enter "e, h" without the quotation marks.