Thomas' Calculus 13th Edition

We match a with $h$, b with $f$, and c with $g$.
$x^4$ and $x^{10}$ can be expressed as $(x^2)^2$ and $(x^2)^5$, respectively. We know that $x^2\geq0$, so neither a nor c is $f$. We can see that after a certain point, $g$ becomes steeper than $h$, meaning that for the same $x$, $g$ will always have a larger $y$. Therefore: a. $y=x^4$ is $h$ b. $y=x^7$ is $f$ c. $y=x^{10}$ is $g$