(b)
$ho(fog)(x) = hof\left\{ g(x) \right\}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = hof\{\sqrt{{(x}^{2} + 1})\}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = h\{\left( \sqrt{x^{2} + 1} \right)^{2} - 1\}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = h\{ x^{2} + 1 - 1\}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = h\{ x^{2}\} = x^{2}$